This is the Marvel universe not DC so you are actually talking about The Avengers. There is an Avengers movie confirmed (2011 at the moment), but apart from Nick Fury and Iron Man its speculation as to which other marvel characters will be in it.
Strongly expected are Captain America and Hulk - although the conversation at the end of Hulk between Stark and Ross is ambiguous as to what Stark is requesting (location of Banner? Ross' help?).
Rumoured - as in where in the Avengers but not yet confirmed as getting their own movie to lead into the 2011 film - are Thor and Ant-Man.
A lot of the Mavel stuff isn't set in stone though...
Stark is in based California in the Iron Man movie. Norton's Hulk was exposed to a gamma ray in the original comic he was in a gamma bomb explosion. Maguire's Spider-Man was bitten by genetically engineered spiders rather than radio active ones.