Wikipedia: Geocaching is an outdoor sport that involves the use of a GPS (Global Positioning System) receiver to find a "geocache" (or "cache") placed anywhere in the world. A typical cache is a small, waterproof container containing a logbook and "treasure". Geocaching is a unique take on a traditional Easter-egg hunt in that it uses two recent technologies, the GPS and the Internet.
If you don't feel like making the financial investment in a GPS, you can give LetterBoxing a try (or just try to find them without a GPS; one person has found over 800 without a GPS at all).
It is possible to rent GPS units http://www.travelbygps.com/travel.php#GPSrental has one option. It's about $25 for a 3-day weekend.
Geocaching in Davis
Davis has lots of geocaches spread all throughout the area. You probably walk by a couple every day not even knowing it. Please don't ruin the fun of the "sport" by revealing the location or details of caches you find. It would also be taboo to map them. Have Fun!
Other Similar Activities
A sister to geocaching, waymarking is about finding and visiting interesting locations. http://www.waymarking.com/
Geohashing is a way of generating a new random point each day at which people may congregate.
GeoQO is software that is being written locally (in Davis) for both GeoCaching and Waymarking.
The River City Geocaching and Dining Society is the nearest huge group that holds monthly events which are fun to attend and for meeting new people.
Yamar (AKA Wes Hardaker) also runs a local mailing list for people in the Davis area. Contact him to get added.
2006-03-11 21:35:32 Waymarking is collecting GPS coordinates for WIFI locations. Wouldn't it be cool to get coordinates to put on the Dwiki and on Waymarking? —JessicaFalkenthal
2007-02-28 01:55:57 There are a lot of wifi networks mapped with GPS in Davis. I've mapped around 400. http://wigle.net/gps/gps/Map/onlinemap2/?addresscode=&citycode=&statecode=AK&zipcode=95616&variance=0.010&s=Show+Address —BradBenedict
2010-03-23 12:48:04 I'm really interested in geocaching. would anyone like to go find my first geocache with me? or help me make and plant one somewhere? —AnniieRose