[shkm]

For most out-of-game tasks you can replace the mouse exclusively with the keyboard. Look into the Vimperator extension for Firefox and perhaps a different window manager if you're on Linux. There are also utilities which let you move and resize windows on OS X & Windows.

As for gaming, you'll obviously need some other special device. You could consider vertical mice and trackballs, both of which a friend of mine is looking into to help with wrist pain.

Oh, fail at me for completely reading this wrongly. Don't post when you're in an instance and waiting for someone to be ressed! I use an MX518 and have for years. It's not the most recent choice, but I love the thing. Also don't forget the importance of good mouse mats -- that is, not promotional ones you get for free.