We are starting a new feature for PC players this week. Bi-weekly community campaigns!

Every two weeks we are going to feature a new community campaign on our servers. We will feature one campaign at a time to make it is easier to find games. We’ll be keeping it featured for two weeks so people can familiarize themselves with the maps for competitive play.

We currently have 120 servers setup around the world with the first featured campaign – 2 Evil Eyes.
http://www.l4d.com/blog/post.php?id=4194

That's pretty cool!