Geohashing is when a random set of coordinates is picked for a longitude/latitude zone utilizing Google Maps. The zones are called "graticules". All you have to do is pick the spot on the map where you live and the graticule appears along with the randomly picked spot for that graticule. You get the spot via GPS.
The coordinate changes daily and it's completely random. On Saturday afternoons if the random spot picked for your graticule on that day can be reached (because sometimes the spot could be in the middle of a lake or other area that can't be reached), people will get together and meet up. This really happens and it's awesome.
Lo and behold there's one I could have gone to today but couldn't because it's 50 miles away and that's too expensive on gas.
If you can see the purple route line (sorry if it's hard to see), I'm on the bottom and the geohash is on top. It's right off US-98 and very accessible.
(sigh..) Win some, lose some. One of these days one will be close by and I'll drive on over. Who knows, I might meet some completely random people that do the exact same thing (a distinct possibility!)