Note: This post will discuss the post-credits scene in Thor. If you haven't seen Thor, and don't want it to be spoiled, then read at your own risk.
Showing that he's been involved in a lot more than just The Avengers, it's been revealed that Joss Whedon was actually the person who directed the post-credits sequence in Thor. (Yes, here's where you can make a joke about that being the reason why the scene was such a waste of time. Slam!) Stellan Skarsgard slipped with the geeky piece of trivia while in Cannes promoting the film Melancholia, telling Empire that he went back to film the final post-credits scene with Samuel L. Jackson, but that Joss Whedon shot it and not Thor director Kenneth Branagh.
Whedon, as you know, is directing The Avengers, and seeing as he helmed this sequence, chances are he did it for Captain America: The First Avenger too. Why Whedon directed it and not Branagh, we don't know. Perhaps Branagh wasn't available to do it, or maybe because these scenes directly tie into the larger Avengers picture, they'd like them to have the kind of continuity that may come with using the same director for as many of them as possible.
The scene is short and extremely barebones (as if there was another scene that was scrapped, with this one added in at the last minute), so it's difficult to get a feeling for Whedon's directing style when it comes to The Avengers. However, with production officially underway on The Avengers -- and San Diego Comic Con looming in the not-so-distant future -- I'm sure we'll see a lot more of Whedon movie magic in the next couple of months.