The comic xkcd suggested way to construct a daily location for each 1 degree of latitude and longitude, where enthusiasts can meet up. I’m getting ahead of myself, so I’m going to quote the wiki:
xkcd comic #426, published on 21 May 2008, contains an algorithm that generates random coordinates around the world every day. Everyone in a given region gets the same set of coordinates. As such, these coordinates can be used as destinations for adventures, à la Geocaching, or for local meetups.
Every day, the algorithm generates a new set of coordinates for each 1°×1° latitude/longitude zone (known as a graticule) in the world. They are randomly placed — they could be in the forest, in a city, on a mountain, or even in the middle of a lake! You can use this wiki to document the daily coordinates (geohashes) you’ve been to.
Unless you can accurately predict the stock market down to the penny, you can’t figure out what the coordinates will be ahead of time. You can first calculate a weekday’s coordinates at about 9:30am ET, and on Friday you can calculate the coordinates for each day that weekend.
When visiting geohash locations, please respect the area you are visiting. Absolutely do not litter or otherwise disturb the natural integrity of the area. However, if possible, creating some kind of a marker out of nearby materials (i.e. cairn of stones, … ‘stick figures’, etc.) is encouraged….
Official xkcd meetups
Official xkcd meetups happen every Saturday afternoon at that day’s normal geohash coordinates. All meetups start at 4:00pm* (local destination time). If you go at these times, you might encounter other readers of xkcd. Bring games!
In such cases when it is unwise to attempt to access the generated coordinates, the Saturday meetup is postponed until a day when the algorithm provides a more suitable location. Alternatively, when the coordinates fall within a body of water, you can rent a boat and win the Water Geohash achievement.