A track-ball to replace my mouse!
 

I'm currently using a Microsoft Intellimouse Explorer. I like it a lot, but I'd like to start using a track ball so I don't have to move my hand around as much. It has a scroll wheel and a "back" & "forward" button for my web browser which is really cool.

If you can recommend a track-ball with similar features, that would be great!

I know there are 3 basic configs for track-balls. Pointer-finger movement, thumb movement, and there is also a model with the track ball in the center, so I assume you could use any finger to move it.