The Raspberry Pi is a fantastic back end to a home automation system. If you'd like to add lights into the mix, blogger Fall Deaf shows off how to use a Raspberry Pi to control lights through a web backend.
The process requires a bit of hacking together, but the end result is a Raspberry Pi-powered light system that you can use your phone to control. The Raspberry Pi runs a strip of LEDs, and the web-based automation system can change what the LEDs do, when they're running and lots more. Head over to Fall Deaf for the full guide.