I recently tried GeoCaching for the first time and I can already tell you that I am addicted. GeoCaching is very similar to a scavenger hunt, but it's on steroids. Users from GeoCaching.com hide GeoCaches and post the GPS coordinates, others then find the cache using the GPS coordinates.
To GeoCache you need the following...
1. An account at GeoCaching.com
2. A GPS device with basic navigation. (Yes, the iPhone will work!)*
* If you are using the iPhone look for the GeoCaching App in the AppStore. I have heard good things about it.
My First GeoCaching Adventure
Please, let me know if you have any comments or suggestions.