Arduino

Arduino is a cheap, open-source microcontroller. (A microcontroller is a programmable chip that can act as the brain of a machine.) Arduino is very populat in open hardware projects, from our CEB Press to Yobot, where it controls yogurt fermentation, to Botanicalls, where it tell you if your plants are underwatered. You can also fabricate one by yourself see:DIY Arduino

http://arduino.cc/en/Main/ArduinoBoardDuemilanove