Instructables has a cool article on using your PC’s screen saver to control the stuff on your desk. That is, once your screen saver flips on, your lamp, radio, and desk heater can all turn off automatically, and turn back on again when you’re back from lunch.
I tend to leave my computer on all the time. It’s a combination of laziness and need. I sit on line quite a bit, and the kids use it as well. I don’t think I’m unique here.
The article gives some good tips (and even code) on how to hook in to the parallel port on your PC. I’d recommend using a USB parallel port out on a powered USB hub (not plugged directly in to your PC) for an extra margin of safety. But only because I don’t like buying new computers.