Additionally, Half-Life 2 and Episode One have been updated with over 40 new achievements. All three titles are currently 30 percent off: HL2 for 7 bucks; and Eps. 1 & 2 for $5.59 apiece. The complete Orange Box collection (with cross-platform Steam Cloud support across all games) is also currently discounted ($21), with the Team Fortress 2 for Mac release promised soon.
Finally, EVE Online: Tyrannis will launch for both PC and Mac later today, making it Steam's first game to launch simultaneously on both platforms.