This is the coolest toy I have seen in a LONG TIME!!!! I want one!

http://www.irobot.com/sp.cfm?pageid=305

The iRobot Create is a basic iRobot Roomba-style bot. It has options to allow you to build your own robot, and does not have the vacuuming or floor scrubbing parts. It is programmable via C or C++ and is also compatible with the Microsoft Robotics Studio.

There's a number of interfaces and some third party companies make some pretty cool accessories, such as a BlueTooth interface for building wireless controlled solutions.

The Flash site is pretty cool too.