Pretty much all USB wheels work on it as far as I know, best mainstream wheel the logitech G25 works, my Logitech Driving Force Pro work great as do the other common Logitech wheels.
Anything logitech works on PS3 (keyboards, mouses, wheels), and im not sure but i think but the pc version of a PS2 controller works i read it somewhere but of course it doesn't have motion-sensing.