Updates to Team Fortress 2, Day of Defeat: Source and Half-Life 2: Deathmatch have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:
Source Engine Changes (TF2, DoD:S, HL2:DM)

• Added mat_viewportupscale and mat_viewportscale to enable rendering the world at a reduced resolution. ("mat_viewportupscale 1" and "mat_viewportscale 0.5" will downscale world rendering by 50%.)
• Added a new convar mp_mapcycle_empty_timeout_seconds to trigger a changelevel when the server is empty
• Added positional audio support for Mumble clients
• Fixed a bug that prevented consecutive clicks on scrollbar buttons
• Performance and stability improvements

Team Fortress 2

• Scream Fortress Event 2012
• Fixed a bug where buildings would be invisible during their setup time
• Mann vs. Machine
  • Added the map Mvm_coaltown_event with a special Halloween mission
  • Fixed a bug where players money would not be set properly when restoring a checkpoint
  • Fixed server crash on vote to restart mission