A few things that have turned out to be fairly economical for me...A lot of these ideas aren't an ideal way to obtain nutrients, but when money is the key short term factor....
Unflavored WPC 80 from BSL. All the whey off Ebay may turn out to be slightly cheaper depending on shipping costs. BSL's shipping it very difficult to beat. Even better, try to strike a deal with a local dairy manufacturer.
For chocolate flavoring, cocoa and a bulk 700 count box of splenda packets is a good compromise b/w economy and good taste. Splenda packets taste better to me than the baking splenda since they contain dextrose in addition to just malto. Cocoa is a must have on my list. One container goes a long way.
Supplements that help control my appetite also go a long way toward saving money on grocery bills. For this reason I invest in Nicotine Gum, E/C, and fiber/fiber-like supplements. Soluble fiber especially has an overwhelmingly nice satiety effect.
Raw Powdered Psyllium Husk (1 lb/$3.90)
Xantham Gum (A 1/2 Teaspoon/Liter fluid goes a long way)
Other options: Grapefruit fiber, Guar gum(tastes like crap)
Another compromise: For oatmeal, I go with Bobsredmill, 25 lb bags of extra thick oatmeal. 50lbs will run a bit over $50 which isn't that cheap but I can vouch for the quality compared to quaker. Buy local and you can probably find another brand for .50 per lb.
Veggies, though a near necessity in most ppl's diets, can be very expensive. I get NOW brand phytofood and veggie carotenoids as a temporary replacement. Saves me a bundle to go the supplemental route here as well. Then I can just take my carbs from cheap sources of grains.
Many specialty items cost a great deal of money unnecessarily. Specifically I refer to the low-cal and low carb diet options. You can obtain ingredients separately and make things like sugar free jams, syrups (Like Cary's) by just seeing what they put in them and playing kitchen chemist.
Minimizing the cost of protein is the hardest thing to do. As mentioned many times already in this thread, cho and fat costs can be brought to nearly nothing. Just something to keep in mind.
