I was thinking it would be cool to use two 2" TFT LCD screens in my Omnibot 2000's eyes so that I could display animate eyeballs. A series of JPG images could be saved to a directory that the computer pulls images from and displays them on the two little LCD displays. One could animate the robot looking around, blinking and moods. You could also program it so that the screens display what the robot sees or even animations like cartoon bombs exploding. It is endless. Sony is doing something similar to this with tiny OLED displays in its new Aibo dog. This idea's tech isn't as sexy as Sony's, but it's cheap.
I quickly put together the following crop sheet of eyes looking forward, up, right, down and left. In reality you would only need one image of each eye position not two as I have displayed.