I use this Armorall wheel cleaner and it works great. Just make sure you don't leave it on too long. Spray it on one rim and then clean that rim and rinse well. If you leave it on too long it leaves a white residue on the rim that is really hard to get off (at least on aluminum). I also use it to get the black carbon build up off my chrome exhaust tips.
http://www.armorall.com/products/vie...ry_index=wheel