Quake Live is essentially Quake 3 played from your web browser. Quake 3 was one of the best first person shooters on the PC for a long time. Currently if you would like to play Quake Live you need to use IE 7, IE 8 or Firefox and you have to be on Windows Vista or XP. I am running Windows 7 in Firefox and the game worked flawlessly. The creators are also working on a Mac and Linux version so that every one can join in the fun.
The game works really well inside the browser and has you go through a tutorial and a practice match while it is downloading some of the files necessary to play the game. This makes it nice because you aren’t just waiting around for things to download. The one downside I have found is the limited screen size. Since the game is inside a browser you are limited to just a few screen sizes to choose from.