For those that have seen The Avengers (which, according to the NZ Box Office, is all of you times two), you're probably aware of the little scene that occurs after the main flashy credits. However, Joss Whedon rounded his troops up to shoot another scene that is going to be slapped on the very end of the credit roll in time for the general US release.
Reports from The Playlist not only back this up, they also claim the post-credit scene to be exclusive to North American screenings.
Well, that sucks.
It doesn't sound like we really missed much however, judging by the scene's description, which you can have spoiled here.