When I get home I'll have to remember to post a picture or 2 of some of my BEAM robots.
Or, better yet, check this out:
http://www.beam-online.com/
So cheap, and kinda fun.
One fun thing to do is to set up an obstacle course, and then set up several desk lamps. The only control you have is to turn the desk lamps on and off to "drive" the robot through the obstacle course.