Valve announces Crash Course, new DLC for Left 4 Dead they will release next month to provide additional content for the zombie shooter. The September DLC release will be 560 points for Xbox 360 and free for Windows:

Entitled "Crash Course," the latest DLC delivers new single-player, multiplayer and co-operative gameplay to both platforms. Targeted for release in September, "Crash Course" bridges the gap between the end of the "No Mercy" campaign and the beginning of "Death Toll" in the original game, expanding the game universe with new locations, new dialogue from the original cast, and an explosive finale

While containing both Survival maps and a Co-operative Campaign, the primary goal of "Crash" is to deliver a complete Versus mode experience in just 30 minutes, resulting in a streamlined version of the game's existing Versus campaigns. A recharge timer for infected teammates has also been added, and item spawn behavior has changed for more balanced gameplay.

"Since the release of Left 4 Dead last November, the design team has been excited about creating new experiences for this world and allowing players to do the same, by releasing much of our internal toolset, like the Survival Pack and Authoring Tools," said Gabe Newell. "We're working with the fans toward the ongoing entertainment value of the product."