Biodiesel.org

“Biodiesel is the name of a clean burning alternative fuel, produced from domestic, renewable resources [like soybeans]. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with no major modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.”

Biodiesel.org is the official Web site of the U.S. National Biodiesel Board. Lots of good info and resources in PDF format.