I first saw Pololu's 3pi robot in action at MakerFaire 2009. It was an impressive and agile line follower with a well-designed compact body. I brought one home and came to realize that it was even quicker than I'd seen at the show.
I took some poster board and electrical tape and laid out a maze pattern. The video below shows the 3pi learning the maze (code available on the pololu site).
The second video shows the somewhat quicker run when the solution has already been discovered.
On the back side of the poster board I laid out more of a racing course with electrical tape. The last video shows high-speed line following after tweaking some of the parameters of the 3pi PID controller.
It's quite a fun little robot. In later orders with Pololu I picked up a nice expansion kit -- which would go nicely with their Wixel programmable wireless module (more on the cool things you can do with Wixels later).