A few ideas:
The game Guitar Hero III. If he doesn't have a gaming system, it's available for PC now.
Again, if he's a gamer, think about buying him a really great gaming mouse or joystick.
There's a great new book: Take Me To Your Leader. It's filled with interesting photos, fun facts, weird info--basically a techno-geek's dream.
http://www.amazon.com/Take-Your-Leader-Ian-Harrison/dp/0756632021/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1197550873&sr=8-1
A Swiss Army Knife with a built in thumb drive for saving computer files or transferring them from one computer to another.
http://www.amazon.com/s/ref=nb_ss_/104-5070294-4799147?url=search-alias%3Daps&field-keywords=swiss+memory&x=0&y=0
An iPod Shuffle--or, if he already has an iPod, some new speakers for it so he can play his music throughout your home.
There's lots of great stuff at http://www.thinkgeek.com -- but you need to order, like, NOW, if you want stuff delivered by Christmas.