If you have Left 4 Dead 2 on Steam, you may have noticed some spontaneous downloading going on this week—turns out a new beta version of a campaign called “Cold Stream” is now available for testing. This four-chapter undead romp takes place in an outdoor setting, and while it’s not heavy on plotlines, you be mauled by a few new enemy types.  The campaign will be included in a DLC pack due later this year (which, as we've previously mentioned, will also contain four campaigns from the original Left 4 Dead game). So fire up the game now and get some free zombie stomping on while you can.  [via Joystiq]