Via Fark: PawSense -- catproof your computer. My favorites:

• "PawSense analyzes keypress timings and combinations to distinguish cat typing from human typing."
• "If a cat gets on the keyboard, PawSense makes a sound that annoys cats. This teaches your cat that getting on the keyboard is bad even if humans aren't watching"

I love the idea that you can teach a cat anything more than, "This is your cat box" or "Feeding time happens at N-o'clock every day."