This is a picture of my dh--he recently celebrated a birthday. I won't tell you which one because we are the same age, lol, and I'm not admitting to it yet. Anyway, he got a new GPS device for his birthday, which renewed our interest in geocaching, a very fun hobby. :-) He came home early Friday, picked up the boys, and went out and found two caches, and then Saturday we went out to our local nature preserve and found three more. Fun! You download information on caches from a site like www.geocaching.com and use the clues and coordinates to find the caches, hidden in a variety of places. There is usually a log book to sign in, and various "goodies" which you can take if you leave more. A related activity is letterboxing, which is very similar except no GPS coordinates are used, just the clues.
It's a fun way to get outdoors, learn some geography, and have fun as a family.