What's next after NXT? need your recommendations

I've just purchased the Lego Mindstorm NXT kit, and I'm impressed.
I worked in robotics some years ago, and it's great to see things like
rotation sensors built into the motors, bluetooth, and a variety of programming languages for the unit.
I have two questions for you all:
- What additional lego products should I use to augment the NXT kit? (and, do most people end up with 2 kits to do real stuff?)
- What books on the NXT do you feel are indispensible?
Thanks in advance for your recommendations! -Paul
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buy "Extreme NXT" (TIA press)
dont buy :-(( "lego mindstorms' NXT hackersguide"
pbr schreef:

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