The first TV spot for Guardians of the Galaxy has been released, part of Marvel’s massive marketing and merchandising push for the August 1 premiere (see "Heavy Presence at Mass").  It warns of an "unstoppable threat," which we assume is connected to the recent announcement that Josh Brolin will voice Thanos (see "Thanos Cast"). 

The last trailer focused on establishing the primary heroes (see "New 'Guardians of the Galaxy' Trailer and Poster").