Many people are using solar panels to generate energy for their home and electronics. Sun tracking turrets are useful for maximizing solar panel sun exposure. RobotGeek has posted a guide that shows you how to build your own sun tracking robot with Arduino.
You are going to need light sensors, a RoboTurret, and a few other parts to get started. The code is available on GitHub. As you can see, the robot can follow a light source automatically.