i deal with both carpal tunnel (diagnosed) and tendonitis. an ergonomic keyboard is a must (i use a kinesis freestyle). one of the most important equipment changes for me is to never use an actual mouse, and to never click a trackpad. instead i use a magic trackpad on my desktop mac, built in trackpad on my mbp, and a logitech trackpad on my pc desktops. all are configured with full gesture capability so i can use the tap features instead of clicking. also, no click-drag. instead i use the double tap to lock feature.

i also mix it up by using my ipad. for browsing, for short emails, etc. the ipad requires different muscles so changes the patterns of use (a good thing).

for exercises, i highly recommend this short youtube video: http://www.youtube.com/watch?v=hUyMNyrOHJQ. i think this was perhaps the best thing for me. it got me out of the worst of it, and keeps me from slipping back to my worst.

i wear wrist splints in bed. this might not be for everyone, but my doc suggested it. a lot of people bend their wrists at night, stressing the muscles and tendons. i was definitely one who did. it helps.

finally, ice. i use ice packs to cool off the arms when i'm hurting. walgreens sells a nice inexpensive pack with a built in cover that works really well. i have 10 of them :)

best of luck.