I built this obstacle with a friend in a couple of hours. It's not much, but it sure is a lot of fun!
The obstacle from the side, with my friend walking by:
Me going over the obstacle:
There's more pictures here: http://altbit.org/pseudorandom/image...able/obstacle/
My bud forgot his skid lid, but we had a great time riding on (and falling off of) this contraption.