Mouse Replacements?

I recently decided to try a non-mouse option for moving my cursor around, a nice new Logitech TrackBall. So far, so good. I’ve tried to move the whole thing a couple times, mouse-style, but for the most part it’s working out great. I’ve gotten used to selecting text and such pretty quickly. On a related not, the iGesture Pad from FingerWorks seems like a pretty nifty invention too. Too bad it costs so much.