Valve's Steam gaming service rolls out Mac version, with free Portal!
Steam's Mac library is kicking off with Valve's own Portal -- available for free until May 24th! -- Sid Meier's Civilization IV, and Runic Games' highly-acclaimed Torchlight. More titles will be added each week, including Team Fortress 2 and Left 4 Dead 2. Also, Portal 2 will launch simultaneously on the Mac and PC versions of Steam. Beyond that, the selection of upcoming games is only speculation at this point.