Global Agenda is 25% off on Steam until Monday, May 31st.

Play the full game for free this weekend only! Featuring cross-platform multiplayer, you can now play Altitude against PC and Mac foes alike.

If you already have Steam, click here to start installing Altitude now. Need Steam? Click here.

Plus, save 50% when you buy Altitude before Monday.

Yesterday when we shipped Steam on the Mac, previous owners of the PC Steam version of Sid Meier's Civilization IV, Civilization IV: Beyond the Sword, Civilization IV: Warlords, Sid Meier's Civilization IV: Colonization, or Sid Meier's Civilization IV: The Complete Edition did not have access to their games when logging in on a Mac.

But as of now, upon logging into Steam, those owners will have access to the Mac version of their games, right in their Steam library.

Pre-purchase Rocket Knight today and save 20%!

Get ready, as Sparkster makes his triumphant return in Rocket Knight, the newest chapter in the classic side-scrolling rocket action series!

Jump in the Call of Duty: Modern Warfare 2 Free Multiplayer Weekend, on now! Also includes double XP earned during gameplay this weekend, plus buy the game before Monday and save!

If you already have Steam installed you can click here to install or play. If you don't have Steam, you can download it here.

2K Games and Valve today announced an agreement to power all PC versions of the highly anticipated Sid Meier's Civilization V with many of Steamworks' features and offer a special Digital Deluxe Edition via Steam. Customers who pre-order the regular or Digital Deluxe editions of Sid Meier's Civilization V on Steam will be rewarded with a free map pack when the game launches in fall 2010.

Sid Meier's Civilization V players will enjoy the benefits of the Steamworks' features included in all PC versions, such as auto-updating, Steam Achievements, downloadable content, ability to access from any computer*, multiplayer matchmatching and more.

Sid Meier's Civilization V Digital Deluxe Edition will expand players' conquests with the new Babylonian civilization and their ruler, Nebuchadnezzar II (c. 630 - c. 561 B.C.). As King of Babylon, gamers will be able to expand their empire with advanced Babylonian Bowmen to rightfully earn the title of Nebuchadnezzar the Great. Sid Meier's Civilization V Digital Deluxe Edition will also include an in-depth "Behind the Scenes at Firaxis with Civilization V" video feature, as well as the game's epic soundtrack.

Gamers who pre-order any version of Sid Meier's Civilization V from Steam will receive the downloadable bonus content, Cradle of Civilization Map Pack: Mesopotamia for free when the game is available. The map pack will let players experience the traditional Western and Middle Eastern "Cradle of Civilization." The pack will include the Fertile Crescent with the Nile River valley to the west and extending east down the Tigris and Euphrates river valleys to the Persian Gulf. Leaders will be able to explore new terrain, cultures and conquests.

For those who can't wait for the immersive experience of Sid Meier's Civilization V, 2K Games is proud to offer a Steam-wide 75% off sale on all previous Civilization titles for a limited time beginning May 6, 2010.

*In supported countries

Now's the time to get your Call of Duty: Modern Warfare 2 ready for the upcoming free weekend. This weekend will feature double XP as well so don't miss out. If you already have Steam installed you can click here to start the preload. If you don't have Steam, you can download it here.

Save 75% off Codemasters Racing Pack, including DiRT2, DiRT, FUEL, GRID, and ToCA Race Driver 3.

Celebrate the Guild Wars 5th Anniversary with 50% off the entire Guild Wars series this week only.

Get started with Guild Wars Game of the Year Edition, the award-winning online fantasy epic. Or check out the stand-alone expansions Guild Wars Factions, and Guild Wars Nightfall.

Or get all three: Guild Wars, Factions, and Nightfall in the Guild Wars Trilogy.

Three epic games. Zero subscription fees.

Be quick! Short and fast sales on your favorite Rockstar Games all week long. Starting the week off, Grand Theft Auto: Vice City is 75% off, but only for 2 hours! Offer ends at 3pm Pacific time. Plus, stay tuned all week for more short and fast sales on your favorite Rockstar Games. Join the Rockstar Community Group for instant notifications on every sale this week!

Or you can go ahead and pick up the Rockstar Collection: 13 best-selling Rockstar Games for 50% off all week long.