A new TV spot for The Avengers has started running, and although there’s definitely some footage that overlaps with the previously released trailers, there’s also some new footage, including a betteer look at the aliens in the film. 
Photos galore have been coming out recently (see "'The Avengers:' Behind-the-Scenes Photos"), and two trailers have been released (see "New 'Avengers' Trailer").  The film debuts May 4th.