One site I'm really interested in with this Hydrogen production project offers lots of EFI and Motor Control circuit designs with parts lists. But sometimes, you run into a circuit on your car (like my instrument panel) or an old OBD I or OBD II that you need to tweak or repair or replace, and nothing but a pencil and paper to scratch out your design with. Or you want to get those fancy Cougar Sequential turn signals on your 1958 New Yorker Wagon. This is a decent freebie! And they sell parts (boards, chips, etc.) http://www.expresspcb.com/
