Recently, a couple friends of mine got a NXT, and they've really got going with it! The two of them, Josh and Josiah, built this awesome car. It's powered via two motorized wheels in the back, and steers the same way that real cars do. They even added the driver with his steering wheel! I especially like the way they installed the US sensor to look like headlights. They also used an ingenius way of doing rack-and-pinion-type steering without any gears:
A motor rotates the top white beam, which in turn steers the axles sticking out on the sides, to which wheels are attached.
View more pictures of it here
Anyway, this was a great first project, nice work guys!
-Jonathan