[Porsche-O-Phile]

Simple Green works great on mine - same with the purple stuff (greased lightning I think it's called) but it's a bit harsher.

I've had great results with citrus cleaners too - although they take a little longer to break all the old crud off. Gunk makes a citrus-based cleaner or go to a bicycle shop - they typically have a nice assortment of citrus cleaners for cleaning bike parts like derailleurs and gears.