There's one product nobody's mentioned in this thread. It works great. It's called Dial soap. It comes in a little bar and you rub it on your hands under a running faucet, then use the resulting suds to thoroughly wash the grime, bacteria, jelly, banana, pizza sauce, chocolate, pretzel salt, boogers, and other detritus off your hands. Do this before you use your computer.
If you do it every time and don't eat or drink while you're working there, it'll go a long way toward eliminating the problem. 🙂, (but I mean it. And - nothing personal!)
Dr. Tom
iMac 1.8 /17" Mac OS X (10.4.4)