Kensington sells a fantastic cordless mouse. It's depth is smaller than any mouse I've ever seen, which makes it a great mouse to travel with. It takes 2 AAA batteries (that last a very long time due to the automatic standby feature) but there is a corded power backup residing inside the mouse. The design is great - the USB receiver plugs nicely into the bottom of the mouse and concurrently turns off the power. No more wasting battery power when you're not even using it. This version of the mouse also has a nice soft rubber surface that makes the mouse easy to manipulate. [$35 retail, $25 at Amazon.com] (5/10/2009)