If you're looking for a way to discover some great Linux games, then search no more: PenguSpy is a Linux games portal which includes both free open source and commercial games, nicely displayed in categories. Each games has a video, description, rating and you can vote and comment on each game.
You'll find a wide variety of games: from the old-school AstroMenace or Teeworlds to new games such as Lugaru, Penumbra Overture and Amnesia - The Dark Descent, classics like TORCS or Super Tux Kart and even online games such as Quake Live. There are also quite a few games I've never heard of - which is a good thing as I'll have a lot of exploring to do.
While overall there aren't too many games available for now, you should find some decent games of which maybe you've never heard of.
Head over to PenguSpy and start gaming.