You may be familiar with the term, "Flash Mob", described by Wikipedia as, a large group of people who assemble suddenly in a public place, perform an unusual action for a brief period of time, then quickly disperse.
Well, now there are World Wide Flash Mobs (WWFM), which are coordinated geocaching events that take place simultaneously at locations across the globe and only last 15 minutes. The idea is the brainchild of the fine people who host the PodCacher web site and podcast show, Sonny and Sandy.
WWFM II was held on November 10, 2007, and over 4,300 people participated world wide. See this video for a high-energy recap of the event.
If this sounds like fun to you, then you're in luck, because WWFM III is set for May 10, 2008, at 10:00 AM! For a list of the different WWFM III events around the globe, use this geocaching.com search. I expect the list will continue to grow, so keep checking to see if there's an event planned near you.