There was an interesting article in today's Boston Globe on this topic.
The Recession and Your Diet: Some Good News - Nutrition and You! - Boston.com
This stresses the idea of cutting out paying for convenience. Cheap convenient food tends to be bad for you, but dealing with big hunks of cabbage, dried lentils, rice, and the like you can make great meals, and not spend a fortune.
If you use meat as more of a garnish than as a base of your meal, you'll find it leaves some money for veggies.
And, buy what is in season, and local, not only is it better for you and the environment, you aren't paying to transport it!
I work right near a large Chinese supermarket, I'm always impressed by how the people there fill up their carts, lots of work is ahead when you get that big mound of something green home, but it's not costing much!