I use a couple of
these for cleaning my rims. Works awesome.
Basically I start out with just a sponge and wet the wheel really well, clean off the major dirt and stuff. Then I just soak the ball in soapy water, and clean the wheel with it. You have to keep dipping the ball in water though, as it has to stay fairly wet. Then I use a clean, dry ball to apply polish if I want to take that step.
(Yea, you read it right. I use both my balls to clean my rims
)