www.ewg.org
Payments Per Acre by Crop
  2002 Farm Bill Average (PAYMENTS/ACRES) 2008 Farm Bill Average (PAYMENTS/ACRES)
Corn 54.37 21.40
Sorghum 41.22 29.68
Barley 28.78 24.28
Oats 0.76 1.09
Wheat 18.02 20.32
Rice 498.77 226.67
Upland Cotton 222.55 130.90
Soybeans 9.83 6.74
Peanuts 438.31 75.80
Total All Program Crops 145.85 59.65
Payment info from CCC: http://www.fsa.usda.gov/FSA/webapp?area=about&subject=landing&topic=bap-bu-cc
Acreage compiled from ERS and NASS data