Got this via the Xbox.com Marketplace RSS feed: Celebrate Bungie Day!
Grab this new multiplayer map free.
Cold Storage Map
Once, the Cold Storage facility was a vibrant, active research center on Installation 05. An accidental contamination resulted in an unforeseen outbreak, which compromised the Forerunner center. Now, emptied and silent, watched only by a local caretaker, the abandoned structure serves as a reminder of how something as powerful as science is ultimately beholden to nature. This new map is available free starting on 7/7.
Downloaded it a few days ago. Haven’t got a chance to try it out yet.