Portable mice for laptops are usually only good for one thing: giving you an eagle claw hand. Belkin's Comfort series of mice supposedly helps that—because it has comfort right in the name.
There are three flavors, one wireless, one Bluetooth and one with a retractable cable. The wireless is $30, Bluetooth is $50 and Retractable is $20. We're big fans of mice, but would rather go with a trackpad than give ourselves permanent damage with usual travel mice. Hopefully Belkin's bridges the gap between usability and portability. [Belkin]