PSN users got a surprise with the early release of the Batman: Arkham Asylum demo last night. The demo became available today for Xbox 360 and PC (PhysX enabled demo).

Other new content on the PSN includes demos for Rag Doll Kung Fu: Fists of Plastic, Crystal Defenders (a Final Fantasy themed tower defense game, full version also available for $10) and Worms.

A third map pack for Call of Duty: World at War is also available for $10.