Ethanol is used inf Flex Fuel vehicles, I think the government is required to buy a certain amount of those a year... and runs in a modified gasoline engine (I've seen mostly tauruses with it).
Biodiesel will work in any diesel engine, usually with some slight modifications to account for it's particular characteristics (I hope to use it in my jetta in 2 years once the drivetrain warranty is done).
Neil Young is currently on tour, and his whole tourgoup is running off biodiesel.
And here is a guy who thinks the whole US could be made to run on biodiesel from algae:
http://www.unh.edu/p2/biodiesel/article_alge.html