Valve has announced that Portal 2 DLC,called ‘Perpetual Testing Initiative‘ is due to be released on May 8th for PC & Mac. The DLC will be absolutely free.
The Perpetual Testing Initiative enables players to construct their own puzzles and share them. The puzzles can be published onto the Steam Workshop, where other Steam players can rate them if they wish. Valve has also said that some puzzles can be automatically downloaded and installed inside Portal 2.
No release information given for the DLC for either the PS3 or Xbox 360.