Quakelive open beta

Quake Live (formerly known as Quake Zero) is now open beta. 30 maps, 40 arenas and extras. Sign up at www.quakelive.com. Start gaming as soon as you get through the queue.
The game modes are:
Duel
Player versus player (1on1) combat. Whoever gets the most frags before the time is up wins.
Free For All
Players engage in a match, where everyone fights for himself. Whoever hits the frag limit the game ends, and this person wins. When the time limit expires, the match will also end.
Team Deathmatch

Quake Live (formerly known as Quake Zero) is now open beta. 30 maps, 40 arenas and extras. Sign up at www.quakelive.com. Start gaming as soon as you get through the queue.
The game modes are:
Duel
Player versus player (1on1) combat. Whoever gets the most frags before the time is up wins.
Free For All
Players engage in a match, where everyone fights for himself. Whoever hits the frag limit the game ends, and this person wins. When the time limit expires, the match will also end.
Team Deathmatch
Same rules, in this mode, two teams fight each other.
Capture The Flag
Each team has a base, holding a flag. To earn points and win the game, a team has to take the opposite flag, and return them to their own.
Clan Arena
Teambased gameplay, everyone starts fully equipped with full armor and weapons. When fragged, the player must wait for the next round to begin.

Lots of stats, leaderboards, and ways to play/compare with friends. This is a fun first person shooter that you can play anywhere that you have access to a web browser.