I did a project in high school where I used the parallel port to control remote control cars. It worked really well; I could record a pathway down the hall, and replay it almost perfectly. You can't access the parallel port without an external library under NT/XP, but you should be able to under (U|Li)nux.

You can actually set individual pins to be on (+5) or off(0), and the response is really quite fast. You can also check pins that detect when two of them are briged, so you get sort of a "switch" mechanism.

Hope this helps.