Have you got a free weekend available? To celebrate Halloween, Valve are unleashing Left 4 Dead 2 on the world. Starting today, the entire game will be free to play for the whole weekend via Steam. New players can begin pre-loading now. For long time players, it is time to welcome your new found friends and help them survive the zombie apocalypse. This is a limited offer and will finish on Monday, 10am PDT.
Via L4D Blog