For anyone heading to Iron Man this weekend (or anytime), according to SHH there is a scene after the end of the credits - so stick around!
EDIT: It was briefly on YouTube (or maybe still is somewhere), and apparently involves a certain cameo that had been rumored. I'll leave it at that for the spoiler sensitive. Also, it says in the same article at SHH that if the movie does as well as they are hoping, they are expecting Iron Man 2 in 2010.