Hunting & Gathering

Treasure Hunting
The objects seeked in the various games of treasure hunting can be divided into three categories. First you can look for garbage made by man. This garbage could artifacts left by ancient societies that get dug up by archeologists. It is be rare coins dugs up by metal detectors. It could be artifacts at a wrech dive. Or on a less profound note, the garbage can be real garbage that you pick up as part of a trail clean up effort. The second type of treasure is natural geological treasures. This could include gold found by sifting rivers. Or ancient fossils found by paleontologists. A third type of treasure is deliberately placed man-made treasure. This could be caches put out by geocachers or letterboxers. Or the caches could tell you to look for landmarks not put out by the cache creators.

Geocaching
With geocaching you use a GPS (Global Positioning System) unit to find a cache of items left by another person. When you find the cache you can exchange an item in the cache for one of your own. While the GPS unit gives you a position for the cache it is still a challenge to find a cache at times -- you have to figure out how to get the cache in the first place and when you are on the coordinates you may still have to search a small area in the target area. As of October 31, 2004 there are over 120,000 active caches worldwide.

Here are some variations as listed in the Geocaching FAQ :

Offset Caches - They're not found by simply going to some coordinates and finding a cache there. With the Offset Cache the published coordinates are that of an existing historical monument, plaque, or even a benchmark that you would like to have your cache hunter visit. From this site the cache hunter must look around and find offset numbers stamped/written in or on some part of the marker site, or continue based on instructions posted to geocaching.com
Multi-caches - The first cache gives coordinates (or partial coordinates) to the next location, or multiple caches have hints to the final cache.
Virtual caches - A cache is actually an existing landmark, such as a tombstone or statue. You have to answer a question from the landmark and let the "cache" owner know as proof that you were there.
Locationless (reverse) caches -- Locate a specific object and log it's coordiates.
Mystery or puzzle caches
Webcam cache
Event cache
Letterbox hybrid

The global resource for geocaching: http://www.geocaching.com/

Letterboxing
Letterboxing is less common --about 1/100 the number of caches worldwide than geocaching-- but the idea is similiar
http://www.letterboxing.org/

Metal Detecting
http://www.accuratelocators.com/

http://www.airsoftpro.net/Merchant2/merchant.mv?Screen=CTGY&Store_Code=AP&Category_Code=Intro Airball (bb s)