Like Brian said, my main passion in life is Parkour. More abstractly though, any sort of movement. Gymnastics, rock climbing, juggling, spinning poi, ice skating, waterskiing (a bit of wakeboarding, but our boat isn't the right kind of boat to be able to trick off of it. Much to my dismay. Then again, our boat is also dead now...), etc.
I like to study new movements and figure them out. Figure out how and why they work, and then work to be able to do them. My most recent interest is figure skating. I watched a TON during the Olympics, and I've gone out and skated a few times since then and really figured out quite a bit about spinning (which is one of my two favorite things in the entire world: Spinning and sliding).
Brian (based on your Pokemans thread) - I totally get where you're coming from in your argument. I used to be a kid who really just kind of sat in front of the computer or watched TV all the time. I really enjoyed reading, but didn't do a lot of it. I really just kind of wasted a fair bit of my childhood, and I really regret that. Now I don't even own a TV (although we're using one we found as a divider in my room), and while I still spend (probably still too much) time on the computer, it's more productive and I spend probably an equal amount of time outside.
When I have kids, (other than using them as behavior and psychological experiments) I really hope raise them in a way where television really just isn't a part of their life, and where all the values we seem to have lost (physical play, exploration, building things) are emphasized.
I think a lot of kids who fall into that situation just have to find something they are passionate about, and then it can start to change their life.