Here is a list of chemicals you can find locally. Might be useful for all you wanna be chemists like myself.
Acetaminophen generic Tylenol, grocery store/drugstore
Acetylsalicylic acid - aspirin, grocery store/drugstore (may require purification from binders and fillers for some purposes)
Acetic acid, dilute available as vinegar at grocery stores. Buy the cheapest white vinegar you can find; you don't want the flavorful organic traces of the more costly brands.
Acetic acid, glacial (concentrated) photo chemical
Acetone available as a solvent in paint stores/aisles and as an art supply.
Aluminum, foil - pretty obvious, at the grocery store. Be aware that most foil will not be pure aluminum but will contain small amounts of other elements such as silicon and iron.
Aluminum, powder - available as a filler for certain mixtures used with fiberglass; found at fiberglass suppliers (you may want to look online). The powder may come coated with some waxes or oils; these can generally be removed with cautious heating in an oven (BEWARE: aluminum powder is a flammable solid that burns with great heat once ignited) or rinsing with acetone.
Ammonium bifluoride, solution - hardware stores, as toilet bowl cleaner/rust stain remover
Ammonium hydroxide, dilute this is clear household ammonia. Beware, you don't want perfumed, colored, cloudy, or sudsy ammonia. Before buying, pick up the bottle and shake it. If it forms suds, you don't want it. I found plain, clear ammonium hydroxide at the local Thriftway as "Western Family Clear Ammonia."
Ammonium hydroxide, concentrated you can purchase a far stronger ammonia solution as a blueprint supply; search online (I've never seen a local blueprint supply store). This is not as concentrated as ammonia can get in water, but it is quite strong.
Ammonium nitrate available as prills at larger agricultural centers, in large sacks. You probably don't want to buy so much. Besides which the salespeople may be suspicious, since ammonium nitrate is easily converted to a blasting-grade explosive. More manageable amounts of ammonium nitrate (at much higher unit prices) can be found inside of instant chemical cold packs found in pharmacies/health aid aisles. Carefully cut open the outer plastic bag without puncturing the water bladder within, and store the pellets in an airtight container, since it is quite hygroscopic (absorbs moisture from the air).
Ammonium persulfate used to etch printed circuit boards; electronics store (catering to professionals; not Circuit City) or online
Ammonium phosphate available as a fertilizer, from agricultural/garden centers. I have actually seen this in chain stores too. Of course, you're once again stuck with a large container. Ammonium sulfate another fertilizer that may not be too difficult to find.
Borax see sodium borate
Boric acid available from drugstore; I found mine at Bi-Mart.
Calcium chloride may be sold as a granular de-icing mixture at hardware stores; also sold as moisture absorbant in smaller containers.
Calcium carbonate chalk, marble, limestone - find these and you've found calcium carbonate.
Calcium hydroxide hardware store, garden supply center; may be called "lime," "hydrated lime," "slaked lime."
Calcium hypochlorite "shock treatment" chlorinating agent for pools. The purity varies considerably according to brand (examine the label). The purest materials may be hard to find outside of a dedicated pool/spa center.
Calcium nitrate a fertilizer - again, one that you're not likely to find at the local Target.
Calcium phosphate fertilizer
Calcium sulfate zounds, another fertilizer
Carbon, bulk charcoal. Get activated charcoal (expensive; drug stores) or natural lump charcoal (found near charcoal briquettes). Do not get charcoal briquettes. They are full of grit and binding compounds.
Carbon, rods welding supply shop or the inside of non-alkaline dry cell batteries (increasingly hard to find these nowadays)
Carbon dioxide, solid "dry ice," useful for low-temperature condensations and (rarely) as a chemical; often found at party supply outlets. I get mine from the nearest Baskin Robbins.
*Caustic soda, found in crystal Drano, and other brands of drain cleaner.
Dextrose drugstore, health food store, even (some) well-stocked grocery stores
Diammonium phosphate - nutrient for wine fermentation. I found mine in the brewing/wine section of the local Thrifway. Hooray for the Northwest, land of DIY alcohol!
Copper sulfate root killer, available at hardware/general stores, usually in the plumbing section; also at some pharmacies.
Citric acid I found mine in the drugstore section of the local Thriftway. But it was expensive - $9.00 for 113 grams! I have since found that citric acid is sold in conjunction with home soap making (search online) for far less. It is also a photo chemical and used in brewing. Some grocery stores may stock it (one alternate name is "sour salt.")
Corn starch baking aisle at grocery store
Diammonium phosphate nutrient for wine fermentation. I found mine in the brewing/winemaking section of the local Thrifway. Hooray for the Northwest, land of DIY alcohol!
Dichloromethane, is found in chemical paint strippers (not the newer, less-toxic ones); it is generally mixed with another chemical or even multiple other chemicals. For some purposes it may be used as-is. For others it will need purification (not covered here). Look in paint store/aisle or hardware store and read the labels on the cans of paint remover.
Ethanol most famous of all alcohols. The stuff people like to drink. You can purchase denatured alcohol as a solvent and fuel in paint stores/aisles, and this is mainly ethanol, but such alcohol also contains a significant percentage of methanol, which may interfere in some reactions. 95% pure ethanol (the remainder is water) can be purchased at liquor stores under a variety of names; the most famous is probably Everclear. You will, of course, need the cooperation of someone 21 or older, and it is pretty expensive due to heavy taxes. It would also be a good idea to explain beforehand to parents why you need this.
Ferric (iron) chloride etchant for printed circuit boards; good electronics store or online (not Circuit City); I've seen it at Fry's Electronics.
Hexamethylenetetramine, solid fuel tables for portable stoves, barbecues, and campfires; found in sporting goods stores/aisles.
Hexamine see hexamethylenetetramine
Hydrochloric acid sold in paint stores/aisles, hardware stores, pool centers, agricultural centers, as "muriatic acid." As sold it is usually quite concentrated and will emit fumes of hydrogen chloride so it's not a great idea to use it indoors.
Hydrofluoric acid, dilute sold in grocery stores (cleaning aisle) and some hardware stores in brown plastic bottles as Whink rust stain remover. It is quite low concentration as sold; nonetheless, make sure you really do heed the safety warnings on the bottle.
Hydrogen peroxide, dilute grocery stores and drugstores
Hydrogen peroxide, less dilute sold in hardware stores, paint stores as part of "2 part wood bleach" kits or solutions. This hydrogen peroxide is generally between 30% and 40% concentration, as opposed to the 3% antiseptic solution from the drugstore. Thus it is not "concentrated," but it is far more potent than your garden-variety peroxide. Caution is definitely advised. You may be forced to buy 2 bottles of solution together in a kit when you really only want the peroxide bottle. The other bottle usually contains a solution of sodium hydroxide, sodium silicate, or a mixture of the two. Locally, at Portland Paint and Supply, I have found that "Daly's" brand wood bleaching solutions are sold unbundled, so I can just buy as much peroxideas I want without wasting money on the other solution. Solutions of 30% concentration, of very high purity (and no stabilizers! ) can be ordered from a variety of places online. It seems to be used as a sort of home remedy for everything under the sun, so you might check health food stores also. Solutions in this approximate strength range (not as good as wood bleach, but close) can also be found at pool/spa centers. Salon centers sell concentrations between 6% and 12% for bleaching hair, but it is weaker than all of the above sources and fairly expensive too.
Iodine, tincture you know as well as I do that this is found in a variety of drugstores or pharmacy areas. Can be purified to yield solid iodine or used as-is for some experiments. The related "Betadine," which comes in larger containers, might be substituted for some purposes. Very large containers of iodine tincture may be available at agricultural supply centers for animal use, but you risk suspicion, since this has recently been a preferred iodine source for drug labs.
Iron oxide pottery supply
Iron sulfate pottery supply, some agricultural centers
Isopropyl alcohol grocery store, drugstore; many places stock 99% purity now, so get it in preference to 70% or 91%.
Lithium carbonate - pottery glaze material
Lithium hypochlorite - rare chlorination chemical; likely impossible to find outside of a dedicated pool/spa center or online retailer.
Lead easily found as balls and wire in sporting goods store/department
Lead oxide pottery/ceramics; may be sold as "red lead" or "lead red."
*Magnesium, found in camping stores as "firestarter bar".
Magnesium carbonate drugstore, perhaps some sporting goods stores
Magnesium sulfate "Epsom Salt(s)," often found at grocery store or drugstore; pottery supply; photo chemical; may also be sold as fertilizer.
Manganese dioxide pottery supply, fresh dry cell batteries (they need to be carefully disassembled and the black material removed).
Methanol this is the simplest alcohol of them all. Found as automotive gas-line antifreeze and water remover ("Heet" or similar), also available as photo chemical. If you just need a little bit and don't mind it being highly diluted with ethanol, denatured alcohol works.
Methylene chloride see dichloromethane
*Naptheline, found in mothballs bought in hardeware stores
Nitrogenous matter, organic once in a while books (especially older ones) may call for or reference "nitrogenous organic matter." Basically, this means anything that came from living creatures that has a considerable amount of nitrogen (usually indicates proteins) in it. Blood meal, made from dried animal blood, generally fits the bill. It is available as a fertilizer at many garden/agricultural centers (including ordinary chain stores). Oxalic acid available as fairly pure crystals in the form of wood bleach powder; found in hardware stores and paint stores/aisles; photo chemical.
Potassium bromide photo supply; for some reason this is much cheaper than the sodium salt.
Potassium carbonate also known as pearl ash, or potash; may be found in some pool/spa pH raising products; used in pottery/ceramics; photo chemical; clean hardwood ashes contain a considerable amount (but for most purposes would want purification).
Potassium chloride found as a sodium-free alternative to salt in materials for softening hard water (found at supermarket, hardware store); beware that it comes in big sacks. May also be found in big sacks as fertilizer. Found in more convenient sizes (and greater unit price) as salt substitute in grocery stores; check label to make sure there is no sodium contained; also photo chemical.
Potassium dichromate pottery, photo supply
Potassium hydroxide, solution the main (only?) ingredient in some drain openers; check the label to be sure it's not sodium-based or an acid opener; found at grocery stores, hardware stores.
Potassium iodide photo chemical, also sold (generally as pills, sometimes pure) as an emergency supply to help prevent the body from absorbing radioactive iodine in case of a nuclear disaster (look at stores, online or off, catering to survival gear).
Potassium nitrate found as fertilizer in large quantities, also as stump remover (found at garden centers) (this is my favorite compromise between price, size, and quality: $3.75 for a 5 pound box with some impurities); found at some drugstores (good purity, also expensive); may raise suspicions due to popularity of making pyrotechnics/smokebombs/black powder). Sold as a ceramic glaze component.
Potassium monopersulfate pool/spa non-chlorine shock treatment
Potassium permanganate sold for manually recharging water iron filters; I found mine at Sears in the plumbing section. I have checked around though, and not all Sears stores have it. So if a local Sears doesn't have it, order it from Sears' web site, or obtain it as a photo chemical (more expensive, though neither is exactly cheap). I believe that it was once found in drugstores, but I have never found it there. This may be another eye-raising chemical, since it can be used for fireworks/explosives and drugs.
Potassium phosphate fertilizer
Potassium sulfate fertilizer
Saltpeter see potassium nitrate
Silver nitrate photo supply or pottery; this is a very expensive chemical, so expensive that's almost worth buying some bullion silver and dissolving it in nitric acid yourself (pure silver is less than $6.00 an ounce and this chemical is more than $20.00/ounce).
Sodium bicarbonate "baking soda," grocery stores
Sodium bisulfate pH lowering chemical (solid) for pools
Sodium borate available as "laundry booster" for washing clothes; also used as flux for torch welding and ceramics
Sodium bromide sold in small packets for initial bromination of spas; also a photo chemical. Either way it's not cheap.
Sodium carbonate "washing soda" used to aid washing of clothes (grocery store, cleaning aisle); also sold as pH raising chemical for pools.
Sodium chloride ordinary table salt; don't get the iodized variety; you may want to recrystallize the salt to purify it of anti-caking agents (or try kosher salt if you can find it).
Sodium hydroxide grocery store or hardware store, sold as Red Devil Lye; small pellets in plastic bottle.
Sodium hypochlorite, solution liquid bleach, sold at grocery stores, or "liquid chlorine" (more concentrated) sold for chlorinating pools; both contain a good deal of sodium hydroxide although the bottle won't list it.
Sucrose this is ordinary white sugar
Sulfur may be available at drugstores as "flowers of sulfur"; sold for agricultural/garden use as dusting sulfur. The dusting sulfur may have up to 10% non-sulfur materials in it.
Sulfuric acid, concentrated when I first discovered this source I practically did a little jig because sulfuric acid is such a commonly used chemical, yet hard to obtain (or so I thought). There are a number of "professional strength" drain opener liquids that contain sulfuric acid. They are not generally found in grocery stores, but should be in any decent hardware store with the plumbing things. Some brands are more concentrated than others, and some contain dyes and extra additives to protect your pipes. I have been pleased with "Rooto" brand; it seems to be concentrated acid with minimal additives. Other brands that are supposedly good include "Crystal Power," "Instant Power," and "Liquid Fire." All of these are easily recognizable because they come in a plastic bottle enclosed in a heavy clear plastic sack. The concentration of these acids is good (not azeotropic, but greater than 90%) but they may contain substantial impurities, because they are made with waste industrial acid (or so I have heard). Oh, and they really do open up drains like a charm.
Sulfuric acid, dilute sulfuric acid of approximately 30% strength is available as replacement battery electrolyte for lead/acid cells. It is found at automotive stores. Acid of 48% strength is available as a photo chemical. Per unit of acid, these are both more expensive than the drain opener, but should also be higher purity (especially the photographic). I have seen 10% sold as pH reducer for pools, but it's hardly worth buying at that concentration.
Tartaric acid I have seen this sold as a wine making supply
Toluene sold as solvent in paint store/department
Trichloroethylene Sold as Sunnyside Carbo-Sol, available at paint stores; may also be sold under other brand names.
Trisodium phosphate hardware store, cleaning aisle of grocery store. TSP is harder to find nowadays because of marine pollution concerns, so check the label to make sure it's not a similarly-named substitute.
Turpentine paint store/aisle, crafts/hobbies; the turpentine that I have smells deliciously of evergreens, but I understand that there are some varieties which smell foul. The natural stuff is harder to find than synthetic substitutes.
Xylene sold as solvent in paint store/department
*Zinc, can be found in hardeware stores as "moss remover". I have found it in two different forms: Pellets, and sheet (used on roofing).