The National Biodiesel Board is a great source for ASTM qualified biodiesel producers, distributors and retailers:
http://biodiesel.org/buyingbiodiesel/guide/

The Department of Energy offers the Alternative Fuel Station Locator that contains a database of refueling stations for the entire country to find stations offering alternative fuels.
http://afdcmap2.nrel.gov/locator/

NearBio is a FREE service that combines the most comprehensive, verified list of US biodiesel locations (retail pumps) and driving directions with easy access from your cell phone or your computer.
http://nearbio.com/