The links below are to a fun project that I've been working on over the last few months.
Section 1 details cleaning-up the frame and refurbishing a scrapped out Kawasaki KE-175 rolling frame, and adding off the shelf parts to convert to electric drive.
http://www.theworkshop.ca/energy/dirt_e/dirt_e.htm
The next section (just posted Dec 11th/07) is an open source hack of a cheap 36V / 40A controller to either 60V or 72V at 25A, 40A or 100Amps.
http://www.theworkshop.ca/energy/dirt_e/2/2.htm