Quake Live beta is a nice idea. It’s the old Quake III Arena family of games but via a web browser. This version rates you and attempts to pair you up with people with similar skill levels.
It’s also popular: wait times to login are around 30 minutes! I like the idea but I re-purchased all my Quake games on Steam a long time ago. And lately I have been playing FEAR 2 so I don’t really want to wait around for the Quake Live to let me on.
Maybe after I’ve completed FEAR 2 I’ll give this some play time.