A friend recently told me about the hobby of letterboxing where you read a story for clues to a hidden box containing a log, some interesting ink stamps that you then stamp in your book while stamping your own stam in their hidden cache. The modern version of this is called Geocaching (using GPS to find stuff). I thought it would be interesting to do a few in my area with my kids. So, I googled around and found there are a bunch (maybe even some created by a reader here? I thought I recognized an email address but I won’t out the person). But, as I read I realized that my poor ADD brain (and my son’s) may not be cut out for deciphering the clues. Some letterboxers provide clear clues but others tell fancy stories and cover up the clues as best as possible.
I didn’t get beyond my feeble attempt to demonstrate how to use a compass to navigate in the woods (by using the degrees portion of the compass).
I’m still interested in this but we may have to wait til the kids are a bit older.
Musings on Faith and Psychology 
I also just discovered geocaching from a friend. When my Dad came down with his GPS, he took me and two of my children out. We had fun discovering the little caches. On the geocache website, they have the caches marked by difficulty. We’ve only tried the really easy ones, but it was a lot of fun. The clues weren’t that complicated and the GPS coordinates were pretty accurate, though we did have to do a bit of searching (and there was a bit of a learning curve using the GPS that precisely.)
The compass thing would be pretty tough for us, though, too.
I have a GPS, and have done a little Geocaching (finding, not planting). There’s a nice trail of them that wanders through my neighborhood, and I still haven’t found the last two caches on it, so if you want (and can provide young hands to dig here and there….), let me know.
However, I’m not sure geocaching is the modern form of letterboxing, although they probably have a common ancestor, probably in “X marks the spot!”