Quake Live has finally reached the open beta stage and the site is live. id Software has brought Quake to a browser near you, so long as it is IE or FireFox.
Currently the site is being hammered by those wishing to try it out and the queue is about 15,000 people deep. They have had at least one hiccup so far with things but the team is keeping you updated via their Twitter page.
Make sure you get signed up because invites will only be available for a limited time.
We've tried it a few times and the game runs quite well in the browser. It is clear that there is still some work to be done as you will run into a few stutters or a crash here and there. Thats what the beta is for however, so get out there and frag some to help the guys at id make it better.