When you sit in front of a computer for 8 hours a day like I do, and have absurdly poor posture (like I do), then you're just a case of RSI (repetitive stress injury) waiting to happen. Over the summer I bought an ergonomic mouse: the Evoluent Vertical Mouse 2. It only set me back around 50 bucks, and the lack of hand cramps is worth it. Your hand is rotated 90 degrees from a typical mouse position, but this is a more natural position for your body, and therefore less stressful. The learning curve wasn't too bad--about 2 straight days of use--although it's taken far longer for my coworkers who only use it once a week or so if they're looking stuff up on my computer.

While the Mace Windu of mice stopped my wrist aches, my right arm and left wrist decided to make their uncomfortable presence known. So I got an early Christmas present courtesy of the IT department: an ergonomic keyboard [the Microsoft Ergonomic Keyboard 4000, to be specific]. It's got some whistles and bells--a zoom toggle, programmable function keys, and even a calculator button!--which I'll incorporate eventually. Right now, it's a nice relief to not have achy arms :)