I have received some questions about building and programming Sumo robots. I am not an expert on robot Sumo and have not entered any official competitions (perhaps others can comment and include relevant links for beginners), but I have led several simple Sumo-like activities in the Robotics Club that I teach at our school, and they are always popular and easy to build upon with further ideas (right now we are doing a sort of robotic Karate/Mixed Martial Arts challenge, perhaps I will blog on that later). Anyway, I have posted this simple NXT Mini Sumo Bot project to show how easy it can be to get started with something like this.
For off-season FLL teams, it is easy to do a Sumo-like challenge by turning the FLL mat over and using black electrical tape to mark out an octagon-shaped ring. Give it a try and see what your kids come up with!