It's a Multiplayer Online Role playing game for PS3 and PC where you create your own superhero (or villian) and fight along side DC characters in the DC Universe. Its been shown that it has TONS of characters, even more obscure ones. If you've heard of City of Heroes, it's like a more advanced version of that set in the DC universe. So far, the powers look pretty sweet too.
It's supposed to be out this Christmas season or early 2010.