Your geek works in front of a computer all day, but yearns to be outside skiing or something. Here are some gift ideas for that type. (Also, this is a highly personal list, so please add ideas to the comments.)
The cheapest MP3 player you can find: Everyone has a nice one. But if you're roughing it up outside, you want to bring a crappy one and you want it to be somewhat disposable. SanDisk has some on Amazon. I used to use an iPod shuffle 'til they removed the buttons. For sports involving gloves, things with big buttons are best. A good stocking-stuffer, but explain it as such so you don't look like a cheap arse. [Amazon]
Nike + iPod Sport Kit: If you like running, the Nike Plus informatics system will track and log and compare your mileage with that of your friends. (I hate running.) $48 at the Australian Apple store [Review; Nike + iPod Sport Kit]
Remember, though, that Nike doesn't map your routes. If you've got an iPhone, I recommend Motion X GPS Sport app for tracking all sorts of outdoor activity routes. $4 [iTunes Store]
Rugged Cameras: The W80 Pentax is pretty compact, takes OK photos and videos, and is shockproof to a few metres, cold-proof to -10C and waterproof to 4.8m. I like it for winter sports. $US300 [Review; Pentax]
Don't forget to recommend your own favourite outdoor adventure gear in the comments.