Climber here too. It's one of the few things I've done where it can grab 100% of my focus and attention. I can't think of anything else I've done that I can do without distraction or my mind wondering.
I go climbing with a coworker before work 2-3x a week. The problems in climbing seem similar to the problems in programming, so it's a good physical and mental wake-up for the day.
A ton of other programmers I know climb as well (we had an engineering offsite at Planet Granite in SF a few months ago), and I also see a ton of Googlers and other software people at Mission Cliffs on a regular basis.
Is rock climbing something you can do alone? (Indoors rock climbing or something similar, at least? I guess outdoors climbing by yourself would be pretty dangerous =P.) It's something I've wanted to get into, but I prefer solo activities.
Outdoor bouldering is just climbing small rocks. Find a small rock somewhere and scramble up it. It is as dangerous as you want it to be. If you are concerned about the danger, bring a pad and let people know where you are.
I first got into climbing by scrambling around boulders on the Sonoma coast, mainly by myself. I had so much fun. When I found out that it was an actual sport that other people did, I was hooked.
Indoor bouldering is the loner's form of climbing. Outdoor is feasible too, but even with the small falls I worry about someone being totally alone. Bouldering does tend to be a little more intimidating and requires more upper-body strength, but just take your time and you'll get the hang of it.
edit: I was also curious about this, and created a similar thread a while ago: http://news.ycombinator.com/item?id=862139