HiTechnic have released the building instructions for a new model, this time a small go-kart. This go cart is controlled by a Power Functions remote, that sends commands to the HiTechnic IR-Receiver sensor which in turn communicates with the NXT.
It looks quick and I'm sure would be a blast to play with. Also a nice bonus that it can be built with both the 1.0 and 2.0 NXT sets :)
I Love how they get around not needing a differential (you'll have to watch the video to find out!)
More info here - http://www.hitechnic.com/models
**CORRECTION** The car uses the IR-Receiver, not the IR-Link as I had originally stated. My fault for writing this post late at night!