Steam Sundays regulars know how much fun mods can be. L4D2's "All Mutations Mod" says Hi. Well, there's more: custom campaigns! Please check out the link at the end of this announcement and if you're interested please do install the maps for future Steam Sunday fun.

http://retroids.com/site/showthread.php/329205-Steam-Sundays?p=506204&viewfull=1#post506204