I picked up a Microsoft Explorer Mouse with BlueTrack Technology for my wife for Christmas (really, it's for her). It lists at $80 but I got it for $50. 
The big selling feature is the ability to track over any surface. It works great! You've had it happen. Your on the road, the hotel desk is too plastic and your mouse pointer is jumping all over the place. You put a piece of paper under the mouse but it slides too. Arrrrr. Two other things I like is the NiMH battery charger (the mouse sits on top of it), the warning light reminding you to charge it, and the 30' wireless capability. My personal intelliMouse sits within inches of the receiver which is the size of the actual mouse. The new receivers are thumb drive sized.