The Left 4 Dead Blog has word on a new community-created campaign for Left 4 Dead 2 called Detour Ahead. Here's the deal: "The new featured community campaign for PC players is Detour Ahead. This 5 map campaign offers Co-op and Versus gameplay. While the explosion in the finale will light the night sky, it's the train bridge you will remember." They have an explanation of the steps required to install and play the mod.