Valve announced it will bring its gaming service Steam, the Source gaming engine, as well as its library of games including Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal, and the Half-Life to the Mac in April

Natural Selection 2 is the next evolution in multiplayer action/strategy gameplay and will be targeted for both competitive and public play. New features include dynamically changing environments, a new resource model, flexible game scripting and modes, and new weapons, abilities and upgrades.

Announced in 2007, The Scourge Project, powered by Epic's Unreal Engine 3, is a story-driven 3rd person shooter built from the ground up for co-op squad play, where up to 4 players each experience a personal story, whilst playing together as a squad.

Set 25 years after the events of the original game, Supreme Commander 2 begins with the assassination of the newly elected president of the Colonial Defense Coalition. The CDC members – the United Earth Federation, the Order of the Illuminate, and the Cybran Nation – deny involvement, blame each other, and a galactic war ensues!

Metro 2033, based on Russian author Dmitriy Glukhovskiy's novel of the same name, is a 3D horror/action/survival FPS with elements RPG genre game.

Shattered Horizon is a multiplayer FPS where teams of players experience realistic zero gravity combat and fight to survive in the aftermath of a catastrophic Moon mining accident which throws billions of tons of rocky debris into near-Earth space.

In Aliens vs. Predator, players will have the chance to take the role of the three infamous species: the Colonial Marine, the Predator and the Alien. Each of the three species has its very own distinct story-driven, single-player campaign mode that interweaves with the campaigns of the other two species. Revealed last week, SEGA confirmed that a multiplayer demo will be available on PSN, XBL, and Steam (no standalone download) starting tomorrow.

Valve today announced extraordinary 2009 growth data for Steam, with major increases in accounts (25 million accounts, up 25%), concurrent players (2.5 million), unit sales (205% increase compared to 2008) while many of the year's biggest releases adopted the Steamworks suite of publishing services.

SEGA's Aliens vs. Predator and Napoleon: Total War will ship with Steamworks support at retail and online, including among other features, Achievements, Matchmaking, Leaderboards, Stats, and Cloud. Aliens vs. Predator will ship on Steam and at retail in mid-February. Napoleon: Total War will ship on Steam and at retail in late February.

In Aliens vs. Predator, players will have the chance to take the role of the three infamous species: the Colonial Marine, the Predator and the Alien. Each of the three species has its very own distinct story-driven, single-player campaign mode that interweaves with the campaigns of the other two species.

Set approx. 10 years after the events of the original, the halls of Rapture once again echo with sins of the past. All along the Atlantic coastline, a monster has been snatching little girls and bringing them back to Rapture. You will play as the first Big Daddy as you travel through the decrepit and beautiful fallen city, chasing an unseen foe in search of answers and your own survival.

Mass Effect is a sci-fi adventure set in a vast universe filled with dangerous alien life forms and mysterious uncharted planets. In ME2, Saren's evil army of Geth soldiers has just been defeated, and humans, who are still struggling to make their mark on the galactic stage, are now faced with an even greater peril. Pre-order on Steam and get the Inferno In-Game Armor as reward.

The Steam Holiday Sale is on now through Sunday, January 3, 2010. This year's sale has begun earlier than years past so gamers can save big on last-minute shopping via Steam's Gifting functionality. Gamers can save up to 80% on select titles, with daily and week-long specials running during the promotion. Entire publisher catalogs, like Ubisoft, Rockstar, Take Two, Eidos, Codemasters, are anywhere between 25% to 80% off.

A fast, frantic and mega-bloodbath first-person shooter, Dreamkiller takes gamers inside the dark and twisted nightmares of tortured souls possessed by unknown forces. Dreamkiller is now available on Steam to play for free for the weekend and you can also purchase it for 25% off until Monday!

The Steam Early Holiday has begun, featuring a daily line-up of select games at deep discounts for just one day each. The Early Holiday Sale continues today with eight great deals: Dawn of Discovery (30% off), Quantz (80% off), The Secret of Monkey Island: SE (75% off), Call of Juarez: Bound in Blood (30% off), The Chronicles of Riddick: Assault on Dark Athena (50% off), Mirror's Edge (75% off), Section 8 (50% off), and Evil Genius (75% off)

The Steam Early Holiday has begun, featuring a daily line-up of select games at deep discounts for just one day each. The Early Holiday Sale starts  today with seven great deals: Batman: Arkham Asylum, Fallen Earth, Far Cry 2 and Champions Online are 50% off, Dragon Age: Origins 25% off, while GRID is 75% cheaper. On Friday at 8am PST and each day through Monday there will be a new line-up of deals.

Modern Warfare 2 continues the gripping and heart-racing saga with an unprecedented level of action as players face off against a new threat dedicated to bringing the world to the brink of collapse. Activision has issued a minor patch for MW2 on Steam, improving IWNet matchmaking

Waraming.net announced that its Massive Assault strategy game series is coming to Vavle's digital delivery platform. Massive Assault, Massive Assault: Phantom Renaissance and Massive Assault Network 2 are now available on Steam giving its users the unique chance to fight for global domination in one-of-a-kind sci-fi environment.

L4D2 promises to set a new benchmark for cooperative action games, adding melee combat to enable deeper cooperative gameplay, with items such as a chainsaw, frying pan, axe, baseball bat, and more. After being delayed for a day, the L4D2 PC demo is now available on Steam, only for fans who pre-ordered the game though.

L4D2 promises to set a new benchmark for cooperative action games, adding melee combat to enable deeper cooperative gameplay, with items such as a chainsaw, frying pan, axe, baseball bat, and more.

Modern Warfare 2 continues the gripping and heart-racing saga with an unprecedented level of action as players face off against a new threat dedicated to bringing the world to the brink of collapse.

Killing Floor is a first-person co-op survival horror, set in and around London after a mad scientist’s “specimens” have broken loose and gone on the rampage. On Oct. 22 Tripwire will release the “Level Up” Free Content pack, and to celebrate Killing Floor will be available for free on Steam from Oct. 22nd through October 25th.

In Painkiller: Resurrection you play as an ex CIA Agent and Black Ops Special Unit who has a big problem: during his last job, he has managed to not only kill the head of an illegal drug operation and a slew of innocent civilians, but himself in a fatal mistake. JoWood is offering its back catalog as digital download through Steam, which now offers Painkiller: Resurrection as pre-order throwing in the previous three games in the series for free.

A host of THQ titles are available at special prices this week on Steam. For the 3rd day, all games in the Dawn of War series (original, 2 expansions and Dawn of War II) are available at 50% off their regular price. In addition, the Civ IV Complete pack (includes Civ IV, Warlords and Beyond the Sword expansions, and Civ IV: Colonization) is on sale for $19.99.