Namco Bandai is making a social game for Sword Art Online with GREE. Sword Art Online: End World has characters from the series represented as cards. You create a party, enter dungeons, and complete quests. The game also has "raids" where you team up with other players to take down a boss. Raids can support up to 20 players, so they’re kind of like actual raids!
Sword Art Online: Infinity Moment is also in development for PSP.