The time has come! Despite long since giving up on using Linux myself, I have to say, it's been interesting to watch Valve bring Steam to the operating system. Previously available by invitation only, the Steam beta has now become available to all users. Should you have any questions about setting this up, there's a wiki over here.
At present, there are nearly 40 games playable on the platform, ranging from Team Fortress 2 to Amnesia: The Dark Descent to The Book of Unwritten Tales. It's only a matter of time before that figure starts growing exponentially. We're seeing a lot of independent multiplatform releases, but I'd love to see more big-budget games share the love as well.