Gentlemen, pardon me for interrupting this thread with a salient comment.
This is the primary nutritional database. BUT, I'll warn you that it's super specific. So, if you search for soybeans it's going to ask you what variety, how you cooked them, and how much you ate. But you can play around with it if you want. Just enter a keyword and click submit:
http://www.nal.usda.gov/fnic/foodcomp/search/