This is a QuickTime movie of the first robot I made with my new Lego Mindstorms NXT system that I got for Christmas. (My lovely wife knows I like to get fun toys for Christmas, bless her.)
The overall mobility and steerability are pretty good on this. The center of gravity is a little too high. If I mounted the controller underneath it would be more stable. Right now it just avoids obstacles with the subsonic and touch sensors.