I hack on Firefox -- most particularly the JS engine, but I've hacked on layout, DOM, networking, and other code too. (If you're using a WebKit-based browser, I've hacked out a patch or two for them. If you're using Opera, well, it's difficult to contribute to a program that's not open source. If you're using IE, I pity the fool.)

The picture's me at the end of a southbound Appalachian Trail thru-hike -- most awesome thing I've ever done in my life. I've also thru-hiked the John Muir Trail (excellent scenery and hiking, too short), done the Coast to Coast Walk across England (an enjoyable way to visit England, but not backpacking), and expect to thru-hike other trails (definitely Pacific Crest Trail, maybe Long Trail, likely others). In other crazy outdoor activities, I enjoy biking. My biggest trip crossed the US, 37 days/~3875mi (not enough time, but also barely enough). Loved it all, could have used more time (externally-imposed deadline forced the pace). I think I prefer backpacking to cycling -- more remote, less like normal life.