If you ignore the estimates that all the farmland in the U.S. couldn't produce enough biodiesel to make a big dent in our petro-appetite, biodiesel is pretty exciting--when you can find it. All the tired jokes about pulling up to your favorite Chinese restaurant aren't very funnny when the needle is on "E" and you want to stay green.
Nearbio.com is a free site that tells you where the nearest biodiesel vendor is located and how to get there. It's really optimized for use on a web-enabled cell phone (nearbio.mobi) where its clean text interface is a blessing. You can enter the usual zip code, address, etc. to tell it where to search. The site claims its staff manually scour web sites, industry publications and press releases every day to sniff out new bio fuel pumps and post them within 24 hours of verifying that each is real.