I have been geocaching for almost 7 years now and consider it one of the best sports ever. If there are any other geocachers on AG this forum can be used to chat about anything geocaching from best finds to bad adventures.
If you don't know what Geocaching is (which is the vast majority of you) this video is a great summery of it: [url=http://www.geocaching.com/videos/default.aspx#cat=cat:newbies&vid=-4VFeYZTTYs] I encourage you to join!
I have heard of it, (popular science had an article), and it sounds like an interesting activity, but I am not one for the outdoors, as I am always cold, hot, wet, dry, or any other ailment that can befall you befalls me.
in other words, I have a very narrow comfort zone.
I used to go with my cousin and uncle a few years ago (maybe 5?) but I stopped after a while. It was fun, but I got kind of bored. But recently (I'm guessing due to the Iphone app) people in my school have started going. I went with my friends a few times and it was quite a bit more fun due to not taking it AS seriously.
But yeah, it's pretty cool and I'll probably look for one every week or so.