http://www.quakelive.com/
It's essentially Quake 3 Arena, except it's free and played in a browser (although it'll need a plug-in). You can play it in both multiplayer and singleplayer, although it's primarily a multiplayer first-person shooter. The graphics are great, yet not so high that it requires super system specs. It's a ton of fun, and I highly recommend checking it out.

My name on there is Bittertooth, if you're interested in seeking me out

...Apparently I need Windows XP/Vista and IE/Firefox...? That sucks, wish I could play. :\

Aw I remember Quake. It was so fun.
But sadly I prefer to play some of the other FPS's I own.

I'm trying it out because, well, two things:
1. I'm bored
2. I need a game worth while playing besides Dead Rising 2 and Phoenix Wright and Pokémon.

I suck at games like these, but hey: Why not?

Name's Connec10. Wasn't that hard to guess, eh?

I gotta admit, Quake Live is more fun than ANY of the CoD games.

I've been playing this game since the closed Beta (But the Closed account was deleted, so, yeah...).

I'm liking the Freeze Tag on Silent Night. I've seen that map before, what is it from?

Well hey, we could all buddy up and stuff!