I discovered letterboxing in 2003, and it has proven to be one of my strongest addictions. It is relatively new in the states, but it has actually been going on in England for 150 years. http://www.letterboxing.org
This was from a graveyard I found while I was hiding my Land of the Yankee Fork Series. I love that series. It takes you out through all of these wonderful gost towns and historic spots up in the mountains near Stanley, ID.