I saw Part 2 of this video (YouTube Link) first when I was surfing around and was blown away that you could build a pair of legs using Mindstorms this size that could walk on their own. Then after reading the comments found out that there are wires holding up the walker. (Play it again and look close, and you'll see them.) Either way. This is still a cool project.
Part one was the first prototype. He made a few changes to the second one. Got to Steven Levy's posts on The NXT Step to read a little more about it.
Both parts embedded below:
Crazy Legs: Part 1
Crazy Legs:Part 2
[via The NXT Step -Lego Mindstorms]
[Image captured at from the video: Crazy Legs 2: http://www.youtube.com/watch?v=fJ3svIc4WsQ&eurl=http://thenxtstep.blogspot.com/]