Valve has announced "DLC #1" for Portal 2 and it's going to be free for all the versions of the game! The new content will be out this Summer and will include new test chambers, leaderboards, challenge mode for single and multiplayer and "more."
Got to say, really impressed that the DLC will be free. I mean, that's to be expected for PC and Mac players. It's the console side that I'm wowed with. Also note the title of this DLC has "#1" so we can expect more content down the line. Then again, this is Valve we're talking about and they always support their games long after release. Yes, Captain Obvious to everything I just said, I know.