An update to Counter-Strike: Source has been released. The update will be applied automatically when you restart Counter-Strike: Source. The major changes include:

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 positional audio support for Mumble clients
Added a new ConVar mp_mapcycle_empty_timeout_seconds to trigger a changelevel when the server is empty
Added a new ConVar sv_shutdown_timeout_minutes
Forces a server to shutdown if it has been requested to do so, even if the server is not empty
Fixed a ConVar exploit that allowed malformed values to circumvent range checks
Fixed a con_logfile ConVar exploit
Fixed HTTP downloads on Mac not sending an HTTP referer
Fixed a bug that prevented consecutive clicks on scrollbar buttons
Fixed a bug that was causing intermittent lag spikes for Linux dedicated servers
Fixed a crash while command-tabbing on Mac in fullscreen
Fixed a client crash in the sound emitter
Fixed an audio problem for Mac users
Fixed MOTD sometimes not displaying HTML contents
Improved the performance and stability of the libraries used for in-game HTML display
Performance and stability improvements
Updated to support Big Picture mode