BioBloc is an extremely cool website. The site allows you to build your own three dimensional animals from blocks and then use genetic algorithms to evolve them to learn to walk, jump, run, roll, etc.
The application – made as a java applet – is very easy to use and it has a pretty good help system to get one going.
It reminds me a lot of Karl Sims‘ Evolved Creatures that Wetware wrote about in September, but now we can play ourselves. I urge you to give it a try. It’s tremendous fun.
(Thanks to Joi for the tip)