Acroname stocks a full line of LEGO Mindstorms products as well as some great books about LEGO Mindstorms.  Here's a quick link to all of the LEGO related products. 

We've highlighted a few products that you may be interested in. 

LEGO Mindstorms NXT Kit

LEGO has reshaped the successful Mindstorms kits with a new suite of sensors, motors, software and connection options.  The processor brick is resdesigned to allow many new capabilities and features to the LEGO community.  See the LEGO NXT page for more detailed information. 

Joe Nagata's LEGO Mindstorms Idea Book

Armed with Joe Nagata's LEGO Mindstorms Idea Book and a LEGO Invention System 2.0 (and some other spare parts) you'll be making all kinds of cool new robots.  Have you always want to make a car that does somersaults? Or a robotic centipede? How about a line following beetle or a two legged-walker? Well this book will give you detailed instructions for build those things and more.  With examples from beginner to advanced, there is something here for everyone.