There's a company in my hometown that will pay $.50 a gallon for used cooking oil from restaurants of all types. Of course anyone can give them used oil but you can only get paid for large (drum sized) batches. They have a truck that makes the rounds of all the local restaurants and you can buy biodiesel from them for $3.50 a gallon.
http://www.bentlybiofuels.com
It's almost hard to believe that 5 years ago everyone had to pay to get rid of the stuff.