I haven't spent enough time yet reading through the Environmental Working Group main website or the related Mulch blog [commentary on ag policy] to decide how much I agree with them [or not], but their farm subsidy database is excellent.
Farm Bill 2007 from the USDA
Some data sets from the USDA Economic Research Service
Apologies for the homework assignments, you don't have to read them, they're here more for my convenience than for any other reason. That and I didn't feel like tackling universal health care this week after all, since I don't have any of my own.