I learned about it in Boy Scouts. One of our Scout leaders mentioned it to our Troop at our annual summer camp in Cook Forest, PA. We went geocaching a few times, and I was hooked. My family got a GPS a month later and we've been geocaching ever since.
I recently introduced geocaching to The Beaver Valley Amateur Radio Association, which is the ham radio club associated with our Boy Scout Troop. All of the members are extremely enthusiastic about geocaching, and a few of them have even went out to buy a GPS just to geocache.
Grant
Member of The Beaver Valley Amateur Radio Association, W3SGJ
Eagle Scout, Boy Scout Troop 405