The Solarbotics Sumovore Kit is a strong, modular design with over 500 man-hours of development and 21 prototypes behind it. It has more power, speed, and is less expensive than the Junun Mark III, Parallax Mini-Sumo, and Tab SumoBot.
If you find it annoying to cut the 1m open beam extrusions down to size - you can now rejoice! Open beam precut lengths are here! Offered in a conveniently packaged kit, these precut pieces are ideal for designing all kinds of interesting structures.