This isn't exactly NXT related, but there is an interesting new technology called a Time of Flight Camera:
Apparently it is potentially useful in the field of robotics for mapping 3D environments. I've seen stereoscopic attempts at this, but the results don't look as precise as this new technology.
It could give information such as identifying the precise x, y, z position of smaller objects in the field of view. It could also locate small openings for the robot to travel through and identify if the robot might hit its head or get stuck on low lying objects. And of course, it would be incredibly useful for mapping an unknown environment and identifying objects based on 3D shape.
Sensors are available from a Swiss maker for the low low cost of only $9095.00:
http://www.acroname.com/robotics/parts/ ... 00-CW.html
Microsoft is planning to release this technology (bundled with a microphone and camera) called Project Natal for the Xbox 360 for a much cheaper price. Perhaps we can do some hacking when the time comes.