Ultimate Frisbee (sometimes called Ultimate for short) is a team sport radically different from other sports. Born in America in the 1960s, Ultimate Frisbee is played all over the world.
Ultimate is normally played with two teams of seven players
each-- although far more can play on one field-- and values
spirit and fair-play over all else. Thanks to the
incredible sense of fair-play amongst its players, it is
self-refereed, making officials useless, even at the
highest level of the sport.
For (far) more, check out wikipedia's Ultimate Frisbee entry. You can also go
directly to the Ultimate Players Organization or the
World Flying Disc Federation. Lastly,
ultilinks is a great resource for
"upcoming tournaments around the world".