Jesse Taylor has a must-read post up at Pandagon.
Ha ha! That describes all his posts, as everyone knows.
Anyway, his post on eating cheaply has the potential to become a classic, one of those rare posts that deserve a bookmark all their own. He's posted his favorite cheap recipe with an invitation for everyone else to post theirs in comments. Surely the Cogblog readership can contribute some great recipes there.
And Jesse's quite right that investing in some good dried herbs and spices will really make a difference in the flavor and variety that comes out of your kitchen. That's right, dried herbs* and spices. I know that all the TV chefs and others who don't really have to worry about the cost of their ingredients always say to use fresh stuff, but that's just not cost effective. High-quality herbs and spices don't really suffer in flavor from the fresh stuff in the grocery store, especially because you have no real idea how old that "fresh" stuff is or the ways in which it's been treated to make it look good in spite of age. I like Penzey's Spices, a place that could just be niche store for uptight foodies but actually provides a good service for those who want to eat well and cheaply over the long run.
My personal opinion is that all anyone really needs is some Kosher flake-style salt, good peppercorns and some dried garlic flakes - dried garlic because at least in Kansas City most of the bulk garlic in the grocery stores is already sprouted, having been grown in China and shipped to the American Midwest for some stupid reason. Buy some onions and you're good to go. Of course, if you want to add some rosemary, oregano and cilantro to the collection, you're really doing well. The point, though, is that a lot of very good dishes can be made with nothing more than just these flavoring elements.
Couple other things. . .markets that cater to a specific ethnicity or geographic area can be great sources. The soy sauce, sesame oil and rice wine vinegar are going to be much better than the nonsense in the megamart. Plus, you can get some dried seaweed, ssamjang and some good Korean rice (Rhee Chun is the best), which pretty much make a good meal by themselves.
*Or, as litbrit would surely point out in comments, grow your own. I've grown some amazing rosemary and cilantro in particular, and I suck at gardening. My mother has a rosemary bush in her back yard which not only provides great flavor to her cooking, but also blooms beautifully. And mint tea made with leaves from her backyard is sublime. One of the joys of living in southern New Mexico.