Left 4 Dead developer Turtle Rock co-founder Chris Ashton posted a link in the official forums to download a scrapped campaign level of the game.
The level, dubbed “Dam It” is unfinished, but downloadable for absolutely free, as long as you own the original game. It’s just missing some code. On the flipside, the download also includes two survival maps that were never released. Certainly a treat for fans who are still waiting for the third title, this is not it but it’s a nice little package.
For an automatic install, unzip the .vpk file and launch it. To install it manually, unzip the .vpk file and copy it to the Left 4 Dead “addons” folder.