For you advanced NXT robotics builders here is a challenging book for you; the LEGO Mindstorms NXT Thinking Robots by Daniele Benedettelli - published by No Starch Press.
There are two rather intriguing projects in the book, a Tic-Tac-Toe Playing Robot and Rubik Cube Solver (which will require a USB webcam) – I have never been able to solve a Rubik Cube, maybe this will give me a little incite for solving it (:-P.
Detailed building instructions for the robots are given for NXT 1.0 and NXT 2.0. The author states that the programs are in NXC and are quite involved, so instead of presenting them in the book the author gives you links to download the required software to run the programs.
Overall, the two projects are fascinating, but the book is definitely for the advanced NXT robotics builder and programmer.