Here's a video that shows one of the robots that appear in the Unofficial LEGO MINDSTORMS NXT 2.0 Inventor's Guide. This book is an updated version of David J. Perdue's original Inventor's Guide. For this revision, David revised the theory chapters and I've created the new project section. This includes six robot projects, with building instructions, programs and further exploration activities. All activities can be done with just one NXT 2.0 kit.
One of the robots is the Lizard, which also appears on the cover. It's a four legged animal that responds to different color signals. Blue accounts for normal behavior; Red colors will make it aggressive, and Green is food -- listen to what it says after I give a green signal, he's well raised!