What you're hearing is the collective squee of comicbook fanboys as Samuel L. Jackson announces after the "Iron Man" film credits that he is Nick Fury, Director of SHIELD, and is inviting Stark to something called the Avenger Initiative.
I'm a DC guy but Marvel is doing a better job at setting up its movies. Jackson and Downey are in, and so's Edward Norton as Bruce Banner. They need to get Grace Park as The Wasp, Jensen Ackles as Hawkeye, Doug Jones as Vision, Milla Jovovich as the Scarlet Witch (Brian Krause as Pietro, how's that for geeky reference? Google away.), and Mark Valley as Cap. Maybe get Jennifer Garner as the Black Widow so we can see Downey bash her head in.