Geocaching is a hobby that combines hiking and treasure hunting with the latest advances in portable global positioning system devices. Cachers, as they like to be called, hide waterproof containers -- caches -- and mark their exact locations with GPS coordinates that are posted on the Internet. Other cachers get the coordinates, punch the numbers into hand-held GPS receivers and follow the digital directions to the hidden prizes.

Sounds like a hobby for nerds? No doubt, but geocaching can be stimulating and addictive.