Geocaching as defined by Wikipedia: “Geocaching is an outdoor treasure-hunting game in which the participants use a Global Positioning System (GPS) receiver or other navigational techniques to hide and seek containers (called “geocaches” or “caches”) anywhere in the world”.

For all you geeks out there, see how you can use some nice gadgets to up the ante in the game. Read the Lifehacker Geocaching 101 guide here.