From the Geocaching FAQ:
Geocaching is an entertaining adventure game for gps users. Participating in a cache hunt is a good way to take advantage of the wonderful features and capability of a gps unit. The basic idea is to have individuals and organizations set up caches all over the world and share the locations of these caches on the internet. GPS users can then use the location coordinates to find the caches. Once found, a cache may provide the visitor with a wide variety of rewards. All the visitor is asked to do is if they get something they should try to leave something for the cache.
I began geocaching in February of 2001 after reading about it the previous week and buying a GPS and registering at geocaching.com. I picked a pretty basic model, the Magellan 315, costing around $150. It is a great little unit for this game but much nicer can be had now for the same price or less. As for the cache, Geocaching.com listed several nearby and I chose GC10D also known as "Dinosaur Ridge".
I was excited about the idea of a high tech treasure hunt immediately and hooked when I found my first cache. I hike a fair amount anyway and this gives a purpose to my sometimes aimless wanderings. Plus, this really shows me many areas that I might not otherwise find. People who have lived in Colorado most of their lives have never heard of some the cool spots I have been. Some cache hunts have taken me to Dinosaur Ridge, St. Mary's Glacier, a 1943 B17 crash site, a couple caves, Roswell's UFO Museum and Research Center, Area 51 (well the boundary line at least), and on mountain tops. Sometimes the cache is located within a few feet of where I park, but I prefer those that are difficult to get. I used the B17 cache as the first leg of a backpacking trip.
For my purposes however, I don't find many of the caches to be compelling anymore. Once the novelty of the search wore off, I realized that most geocaches were simply not worthwhile. Given it's popularity I know that plenty of people will disagree, but I am looking for something more challenging. It seems to have been taken over by the lame SUV-dog-walking-soccer-mom-sniveling-brat crowd. Now I really only have an interest in searching for the difficult ones. Sure sometimes I will take a stroll in a nearby park and hit a few easy caches, but the fun for me is a cache that I have to work to get preferably in a wilderness setting.
To that end, I have placed some of Colorado's most difficult geocaches, but since they are require no small amount of work, few have found them. I even made the Rocky Mountain News on 08 November 2003. Unfortunately my two physical caches are history. Missing Streamlet was placed in Lost Creek Wilderness prior to the ban on geocaches and was removed in 2004. An Airy Abseil was in Jeffco Open Space which now requires permitting and Jeffco never responded to my request for a permit. I don't know if I'll ever bother placing another cache especially considering all the flak I got with An Airy Abseil. The cache had to be rappelled to and I deleted the "Found It" logs of some people that did no more than watch their geocaching partners do the drop. There was a huge online "discussion" about how it was a team find and they shouldn't have to rappel. That was the entire point of the cache! How stupid. Even the CO Admin wrote to say that I never stated that to claim it you have to do the rappel. Well duh. The cache box is pinned to the side of the cliff. It never occurred to me that someone who didn't even ever see the cache would claim it as a find just because they walked over to the cliff. So I'm pretty disgusted with the whole lame suburban scene.
Congratulations to those that have found any of my caches!This is my current recommendation for a GPS unit, the Garmin eTrex Summit. However I have non-geocaching reasons for picking this model. Many geocachers may prefer the Garmin Gecko series for its size and the maps. The Geckos are small and right on the money.