OK, first off for all you Ranch Fans out there, it can be made with using non-flavored low or even no fat yogurt instead of the whole milk or cream like it suggests on the Ranch powder directions and the ranch powder itself can be purchased in just about any supermarket, Hell SAM's club sells ranch powder in pretty large canisters, which I love and throw the powder straight on my grilled chx all the time.
Other combos that work really well is using a healthy oil (safflower oil, flax seed oil, extra virgin olive oil, etc) you can mix that with Balsamic, Apple cider (sweet), Lemon/Lime juice works well if you buy some Mexican seasoning and want that taco/fajita kind of flavor. I guess the only other tricks I have found is I have a juicer and I might throw a tad of this that or the other, carrots always being a favorite juice to add to a dressing. The next thing for variety is seasonings, Love me some Mrs. DASH seasonings, then to add salt, I always use sea salt (I personally like a little salt, but salt is optional).
That is my technique, I mean if yall want specific recipes, I would have to know the size of the salad in which I was trying to season and what type of flavor you were in the mood for and then I could come up with some exact measurements, I season and dress my salads as I make them, I just always keep all these ingredients handy to make like 20 different style dressings at any given time. I don't actually make like a bottle of dressing and keep it in my fridge.