We don't really understand why, but Marvel and Paramount have thrown caution to the winds and released some of Captain America's pre- and post-credit scenes. If you haven't watched the movie and have managed to avoid it like the plague, beware, because it's about to get spoilery. (The Avengers are coming!)
Is it weird that the studios are spoiling the end of their own movie? Shouldn't they want people to pay to see this? The good news is that the finale footage from Captain America doesn't reveal the whole scene. There's a little bit of setup before and some dialogue after that's missing, so they didn't ruin it completely.
As for the Avengers teaser, there's a LOT more where this came from. Here they just give you some high-quality face time with the superheroes that'll be dominating your summer next year.
They show flashes of Tony Stark (does anyone else notice his Black Sabbath TV shirt?), Steve Rogers, Bruce Banner, Thor, Black Widow, Hawkeye and Nick Fury. There are also a few characters (heroes and villains) missing from this version that appear in the theatrical cut.
They are leaving something to the imagination. Not much, but something!
Captain America: The First Avenger is currently playing in theaters everywhere.