How would someone go about rapidly turning lights on and off?
Back in October, before I knew about the awesomeness of Instructables, (AKA "The best website ever,") I was trying to make some spooky ambiance for Halloween by having some lights with red color gels turn on and off every half-minute-or-so inside the house, along with some screaming, chainsaw sounds, etc. I attempted to figure out how to do this by asking on Yahoo Answers, and... well.. read it yourself to get the full picture. Realize that one answer was amazingly vague, another simply answered by what I already tried doing, and the community-voted-best answer was joking!
So, I'm a bit curious, but lets pretend it's back in October. How would someone go about turning lights on or off every 30 seconds?