I've been geocaching on/off for years. I found it mentioned on the forum but no further leads. Thought I give more info as I believe we camping/hiking types would enjoy hearing more about it.
For those of you who have a GPS and want an interesting activity while traveling and camping I think you'll enjoy geocaching. It also gives the kids a lot of fun running around in the woods
http://www.geocaching.com/
They also offer "Travel Bugs" that you can release into the wild and then track. Or living vicariously through your travel bug as my wife likes to say. We have one we released last year who's mission was to travel the world. Right now it is in Switzerland.
Here's the photo link to "Wandering Sailor on a delta glider ramp overlooking Drei-Länder-Blick, Switzerland
http://img.groundspeak.com/track/log/20 ... b183d8.jpg