In a move that will make many people happy, Valve have announced
some free add-ons to Portal 2, due to land October 4th:
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.
To "hold you over" until the release, they've also released Volume 3 of the soundtrack, which you can download now
, locally from AusGamers.