I believe the vast majority of US biofuel is ethanol from corn. The corn-ethanol piece of the energy bill, to me, seems like pure pork-barrel legislation by the Cornbelt congressmen (as well as a bit of green-wash). Under current technologies, it takes about as much fossil fuel to produce corn-ethanol as is saved. Sugar cane has a somewhat better efficiency. Greater promise lies in switchgrass (cellulose) and algae.