Did my first letterbox, Watch House this afternoon. Very similar to geocaching but a cool stamp was made onto a sheet of paper (as I can't find my geocaching log book at the moment). Left my own stamp behind on the log book.
In other news I have started to build my first Dublin, Ohio geocache - the box has been found, logbook obtained and a park to place it in found.
As an alternative and addition to geocaching, there is letterboxing where you swap stamps imprints at each letterbox. Looks like there are several letterboxes in Ohio and at least one, leatherlips, I have been VERY close to.