Re. biodiesel - there's 'biodiesel' and 'straight vegetable oil' (SVO).
biodiesel is an EPA-certified fuel that can run in an unmodified
diesel engine
http://www.biodiesel.org/resources/b...s/default.shtm. SVO
is the 'fish shack' fry oil that, when filtered, can be used in a
modified setup (heated tank, some extra fuel lines / switches).
Apparently one can brew his own biodiesel from SVO, but i imagine this
is a PITA.

Marine applications seem to be a great place for biodiesel: it's
limited availability is countered by the fact that a boat takes on a
larger amount of fuel less frequently, and that you can mix biodiesel
with petrodiesel in any proportion.