I'm bullish on algae. I've written about it here, here and here since April. According to Valcent, you get 18 gallons of biofuel from one acre of corn per year, 700 to 800 gallons per acre per year from palm, but up to 20,000 gallons from algae , and that's in an open-pond system. It's much more efficient in terms of volume and other factors if you are in a closed-loop bioreactor. This also gives you the hugely added benefit of sequestering captured carbon dioxide. Valcent CEO Glen Kertz says "If we took one tenth of the state of New Mexico and converted it into algae production we could meet all the energy demands for the entire United States."
