Just head on over to QuakeLive.com and register, download the plug-in, and get fragging. I loaded it up in Linux 3D OS and found it a little buggy. What is your experience with Quake Live on Linux Or Mac so far?
About Quake Live:
Quake Live is a browser plugin-based first person shooter video game developed by id Software, which first appeared in 2007. It is a variant of its predecessor, Quake III Arena, running a slightly updated version of this game's engine. The focus is on usability enhancements rather than graphical upgrades, including the plugin that runs compile code on the user's processor and a more streamlined heads-up display. Notably, this game doesn't make use of Adobe's Flash technology to run. Quake Live is free to play, as financial backing for this project comes from in-game advertising.
Don't expect any graphical wonders from this game; based on a title released in 1999, it's meant to have a quick and simple installation procedure for casual gaming or maybe aid team-bonding through lunch break tournaments.