The companion web site to the book, "LEGO MINDSTORMS NXT ZOO!" features the following:
* Illustrations of all nine models in the book
* A tutorial on parts substitutions for the models in the book
* Downloadable instructions for producing animal sounds for your NXT (for both Windows and Mac)
* Little-known facts about the real animals that the models represent
* A complete parts list for every model in the book
* Links to where you can buy every part used in the book (via Bricklink)
* Lists of other LEGO models that use the same parts as those in the book (via Peeron)
The site is here.