Geocaching: "... began in 2000 when the U.S. government released GPS signals for civilian use. GPS enthusiasts began brainstorming online about ways to use the new technology.
A few months later, a computer consultant named Dave Ulmer hid a plastic bucket in the woods in Oregon and posted the coordinates on a website. He called it the 'Great American GPS Stash Hunt.' Within a few days the bucket was found, and a new sport began.
As of this month, there are more than 575,000 caches hidden in dozens of countries around the world, including some in remote locations in Antarctica, Iraq and Papua New Guinea, according to Groundspeak, the company that oversees the geocaching.com website."