Portal 2’s first DLC has been confirmed to be released October 4th! The DLC includes a new Co-op campaign, as well as Challenge Mode and leaderboards! Here is the full press release, news via Rock, Paper, Shotgun:

"Portal 2: Peer Review" Available on PC, Mac, PS3 and Xbox 360

September 29, 2011 — Valve, creators of best-selling game franchises (such as Half-Life and Counter-Strike) and leading technologies (such as Steam and Source), today announced the free DLC update for its bestselling game franchise Portal 2 will be rolled out across all regions on Steam, Xbox LIVE and PSN starting October 4th. The free DLC, titled "Portal 2: Peer Review", is available to all owners of Portal 2 for download on PS3 and Xbox 360, and will be automatically downloaded via Steam on PC and Mac.

In "Peer Review", you and a friend will continue the story of loyal bots P-Body and Atlas as you puzzle your way through a mysterious new co-op test track and once again match wits with GLaDOS. The DLC also features a single player and co-op Challenge Mode, and leaderboards to compare Challenge Mode scores with friends and the Portal community.

Also, the third installment of the Portal 2 soundtrack is available on the official Portal 2 site. Volume 3 includes songs from the last act of Portal 2 including "Want You Gone", as well as more music from the Co-op campaign. Check it out now!

We also have put up a new Community Spotlight, highlighting of all things one of the best Portal 1 maps Try Anything Twice by long time community contributor, HMW. Install Portal 1 if you don’t have it already (you did get it when it was free, right?) and give it a play!

Lastly, there is an amazing 20 minute long Aperture fan video that showed up on Youtube yesterday. This was really well done and is a lot of fun to watch. Here it is: