Valve has decided to add Linux to its list of supported platforms.
As part of the new initiative, Valve will release a full-featured Steam client for Ubuntu 12.04 in the near future. After that, the company will release a complete port of Left 4 Dead 2 followed by additional first party titles for the same Linux distribution.
Valve’s Linux team is also working on porting the company’s Source Engine to Linux so that third party developers would be able to use it to develop games for the free and open operating system.
For the time being, Valve is focusing its Linux development efforts on Ubuntu. Support for other Linux distributions might get added later. In the meanwhile, you can check Valve’s Linux team blog for updates on their progress.