[TECH] - Rock'em, sock'em robots - This is cool. Robocode is a Java-based project that allows you to program robots (robot tanks, actually) to fight it out in an arena. You program the tanks in Java, within their application. I believe you need Sun's JDK installed on your machine and that's it. I had the application running on my machine in minutes and edited my first robot.
If I had a lot more time, I would definitely be playing with this.