http://www.geocaching.com/faq/
Someone posts gps co-ordinates of a hidden cache, you find it, sign the log, you can exchange items that are in the cache, or just look at it.
They also have Travel bugs, which can be any item, but it has dog tag with a tracking number, and these go around the world via people visiting the cache's, and are tracked online.
There are 1425 of these in qld at the moment.. about 1800 in victoria, 2075 in NSW, didn't look at other states.
I did a search and there are 60 of these things within ten km of my house!
This is going to be fun

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