NXT and Robolab Resources
Here are some useful links for sites related to LEGO, Mindstorms, NXT, and Robolab.
Nxtasy.org: the site of one of the most active NXT development communities.
Nxtasy forums: the best discussion board for Mindstorms I've found. Tons of generous knowledgeable people hang out and answer questions. Tends to be pretty technically oriented, but very friendly.
MINDSTORMS Education NXT: the official LEGO site for Mindstorms educational users. Not that useful for support.
LEGO Mindstorms: another official LEGO site for Mindstorms general stuff. Not that useful for support.
LEGO Engineering: at Tufts University, where a lot of the Robolab and robotics work is done. Some good sample robots and programs if you hunt.
The NXT STEP: A very good Mindstorms NXT blog with many key Mindstorms developers posting.
CMU Robotics Academy: the National Robotics Engineering Center at Carnegie-Mellon. First class, very comprehensive source.
This is just a list to get you started. There are probably lots more sources, depending on the specific aspect of the subject. In general, I have found the non-LEGO sites and communities to be far more useful than the official ones from the company. This is a sign of the great popularity of the product.