What is the name of the bad guy at the end of the credits in The Avengers movie?

Red Skull from Captian America

The previously entered answer, stated above, is wrong. The guy at the end of the Avengers movie is most likely Thanos. You might notice that the guy at the end has more of a purple-ish skin color, and has more of a rounded and fleshed out face; The Red Skull from the Captain America movie has red skin, and has a bony or skull-like face, hence the name Red Skull. Plus if you look at pictures of The Red Skull and compare it with a picture of the guy at the end of the movie, they don't look the same. If you do the same with a picture of Thanos, you will find that they look almost identical.