Where can I find "hacker" information about the NXT? I want to know if, and where, is some extremely detailed hacker information on the Mindstorms NXT 2.0.  Things such as the processor, flash memory, and RAM information, GPIO or I2C support, custom firmware mods, maximum amperage draw, motor types (AC or DC, stepper or standard), sensor details (ultrasonic and color), and all of the other things that hacker types love.  Don't get me wrong, the NXT is incredible as it is, but I would be happier getting one knowing that I have some room to mess around with it.
You can start with the Hardware Developer Kit which includes "documentation and schematics for the NXT and related sensors", supplied by The LEGO group to help you "design and develop your own sensors and actuators [motors] that can interact with the NXT".

I've not really looked at the latest ones, but the original O'Reilly Unofficial Guide to LEGO Mindstorms was very good, and covered things like creating your own sensors for The Robotics Invention System - looking at the descriptions of the newer ones, they don't appear to require soldering irons or alternative programming environments :(.