This little guy Was more a project in making something fun as opposed to pretty. He is based on a Phototropic 1381 circuit. All that means is that it eats light. The solar cell charges a capacitor (big tube under the solar cell). Once the capacitor has charged to 3 volts, a chip "flips" and dumps all the stored electricity into the motor attached to the eyeball. the effect is that every ten to fifteen seconds, the eyeball turns smoothly about 20 degrees. No batteries required.
It's fun to watch people I'm talking to in my cube stop mid sentence when they see the motion.
The Solar cell is from American Science and Surplus (only thing I actually paid for..), the gear motor is from a junked security camera, the base is a hard drive head, the capacitor and some of the parts of the circuit are from an old motherboard. The wire is from a stripped CAT5 cable. The eye is compiled from misc parts I had laying around. If you look into the eye, the circuitry you see is actually a magnified view of a tiny sensor chip from a CD-ROM laser assembly I glued to the back.
The circuit I used is available here: