sounds like a fun activity and perfect to pair with photography ... out there hiking and hunting for "treasure" in the great outdoors. From what I understand some of these "caches" are in beautiful locations.
I just found out about it and I'm thinking of giving it a try. It would be fun to find out if some of you do it. Maybe one day we could combine it with a gathering somewhere.
If you don't know what it is, http://www.geocaching.com/ explains it.