Just a few weeks after Counter-Strike: Condition Zero was ported to Linux, it's now officially available. Counter-Strike: Condition Zero is a decade-old expansion to the original Counter-Strike game on the "GoldSrc" engine.
The game is still fairly popular and sells for about $10 USD via Steam. Even for being a decade-old, the graphics and game-play of Condition Zero can still surpass that of many open-source community-based games.
In the Steam announcement of CS:CZ being official to Linux, they also made mention it's "the fifth Valve title to be released for Linux and, with its release, pushes the total number of Linux games available on Steam to 80."
Valve also says they will be bringing more of their titles to Linux in "the coming weeks and months." Up next will hopefully be some of their more popular and interesting Source Engine games. As I've said before, I fully expect the clear majority (if not all) of Valve's in-house games to be ported natively to Linux ahead of the Steam Box launch later this year.