Updates to Left 4 Dead have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:

Left 4 Dead
* *** Added Mac support for Left 4 Dead ***
* In Versus mode Tanks will spawn in stasis until a human player takes over. Tanks in stasis are invisible and invulnerable, and won't move or attack
* Tank speed is no longer reduced when on fire
* Allow players on the Infected team to manually spawn during finales
* Added a vote option toggle All-Talk
* Any Special Infected that causes a Survivor to stumble into a "ledge hang" situation will receive 50 points
* Bullets that first pass through an infected character before striking a Survivor are now ignored as friendly fire
* In Versus mode car alarms will now trigger anytime a Special Infected pulls or stumbles a Survivor into an alarm car
* Protected console commands that can be used to lag or crash servers

Source: http://steamproxy.com/steamstore/news/4564/

Please come and share your thoughts in this open letter on the Steam Forums.
If you do not have an account and wish to share your thoughts, please take the time to create an account (on the forums) as we are interested in seeing what you think.

Open Letter Thread:
http://forums.steampowered.com/forums/showthread.php?t=1536837

Source: http://steamproxy.com/steamstore/news/4436/

14:04

An update to Left 4 Dead & Left 4 Dead 2 has been released. The updates will be applied automatically when your Steam client is restarted.

The major changes include:
L4D 360:
- Added "The Sacrifice" content.

L4D2 360:
- Added "The Sacrifice" content.
- Added "No Mercy" content.

- Game Play
• Bullets that first pass through an infected character before striking a Survivor are now ignored as friendly fire.
• Fix for survivors speaking The Passing Finale lines in other campaigns.
• Added a setup timer to Versus Survival
• Fixed bug in Versus-Survival where a team could get 5 survivors
• Removed Defibs and First Aid Kits in Realism Versus. Survivors start with a First Aid Kit, but all world spawns are disabled.
- UI
• Added vote option to enable All Talk in Versus.
• Added vote option to Restart Chapter in Versus.
• Added the ability in the lobby for all players to vote on starting the game.
- Versus
• Charger now receives 300 points for any Survivor that is insta-killed.
• Charger now receives 100 points for any Survivor that is insta-incapped by a charge.
• Any infected that causes a Survivor to stumble into a "ledge hang" situation will receive 50 points.
• Tanks go into a stasis when they spawn and leave stasis when the human player takes over.
• Tanks in stasis are invisible but still show a glow to the infected team.
• Tanks do not attack when they are in stasis.
• Tanks in stasis cannot be set on fire or damaged.


L4D PC:
- Fixed a few third person camera cheats.
- Added VPK audio cache support.
- Added "The Sacrifice" content.
- Added Versus Multi-Map Scoreboard
- Added the L4D2 Mounted .50 Cal
L4D2 PC/OS X:
- Game is fully playable on the Mac platform.
- Fixed a few third person camera cheats.
- Added "The Sacrifice" content.
- Added "No Mercy" content.
- Versus: Infected players will get a respawn time reduction against teams that rush.
- Removed need for Left 4 Dead 2 Add-on Support for Community Campaigns

Source: http://www.garrysmod.com/2010/09/24/garrys-mod-for-mac-is-out-50-off/
Garry’s Mod for Mac is out – 50% off!
Friday, September 24, 2010 by Garry Newman

Garry’s Mod for Mac was released late yesterday night. For the most part it seems to work quite smoothly. We had a problem with our servers being DDOS’ed shortly afterwards, which is why the forums are down.

The number one issue reported is that the game crashes when you change resolution. I’m going to have a good look into this, but people are saying it happens in all Source Engine games on the Mac – or may be graphics card driver related. It does happen to me on my test Mac – so I will be able to look into it further.

The celebrate the release we have a 50% sale – which applies to Windows and Mac users (because we’re all the same inside). So now might be a good time to gift a copy to your best friend :)

Well, it looks like we're not going to get it.

http://forums.steampowered.com/forums/showthread.php?p=16678216#post16678216