The "Perpetual Testing Initiative" DLC will arrive for the PC and Mac versions of Portal 2 on May 8. The free expansion will allow players to design their own puzzles, then publish them to the Steam Workshop for review and play by other players.

There's currently no word on when, or if, this content will be available on consoles. The PS3 version of the game supports Steam for multiplayer gameplay, but Steam Workshop support hasn't been announced; there's no Steam integration in the Xbox 360 version.