So I've found a few of these doing trail maintenance and forestry in the rockies on accident, and I remember hearing about them when I was a kid, but how are you supposed to find these things?
There's a website, geocaching.com -- it's free to make an account, and there is a world map showing where geocaches are hidden.
The easiest type (traditional caches) will just have a location on the map where you go to find the container. Some of the more difficult ones, you might have to solve a puzzle before you can find out where you need to go looking
Fascinating, I wonder if the one's I've found before are on there, they were in an area that, while not closed to the public, I've never seen in 3 years of arbory anyone there that wasn't there with me. Deep woods in-between ski trails.