The major players for WVO kits and parts in the USA:
PlantDrive - Highly regarded equipment. Craig is active in the forums and has spent time to answer my questions very thoughtfully.
Frybird - Also highly regarded equipment. Lots of information on website.
Golden Fuel Systems (use to be greasel.com)
Forums:Danalin Scott's Forum on infopop.cc (probably the largest forum I've found, many hours worth of searching and reading)
Danalin's Forum on websitetoolbox.com Valuable diagrams on different configuration possibilities and Kit comparisons
VegOilFuel Yahoo Group Another forum moderated by Danalin. Check out the files section, one of the members wrote up a very nice HOW-TO and created a pdf file for all to use. Here is the file if you want to download it from me. (slow)
Here are some links to other people who have blogs or websites about their WVO conversions: (I haven't digested everything here yet)
Arctic Vegwerks These folks specialize in installed cold-weather conversions. They favor PlantDrive, with Frybird in #2 position.