Steam and Source Coming to Mac

Gaming service expands to Mac platform
Valve has announced it will bring Steam, Valve's gaming service, and Source, Valve's gaming engine, to the Mac. Steam and Valve's library of games including Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal, and the Half-Life series will be available in April. In addition, Portal 2 will be Valve's first simultaneous release for Mac and Windows.