http://www.twitch.tv/rebellion_official if you're on PC, then Zombie Army Trilogy has just been updated to give you the chance to play as Left 4 Dead 1 or 2 characters for free. no word on if consoles get the update for free yet. the website(zombiearmy.com) has a free comic that explains how the L4D crew got into the apocalyptic alternate 1940s.