Ours is made from 1 1/4" PVC conduit left over from the tetrahedrons in 2005.
http://www.flickr.com/photos/jrhicks...7604319698768/
It is sturdy, light, and knocks down to fit in the back of a minivan. It was designed and built by Jeremy, third from the left. I doubted it would be strong enough, but he was more than happy to prove me wrong. If students on my team actually listened to me, we'd still be building mini-sumos!
Jason