The earliest public screenings of Iron Man are now underway, and thanks to early reports it is confirmed that Samuel L. Jackson has a cameo appearance in the film as Nick Fury of S.H.I.E.L.D. Thanks to Moviehole we have a report of the final scene (which occurs after the credits) and that Jackson's appearance sets up a possible Avengers movie.
According to the report, after the credits are finished a forty-second or so long scene plays out. Tony Stark (Robert Downey, Jr.) returns to his apartment to find Nick Fury (Samuel L. Jackson) sitting there. Stark asks Fury who he is, and Fury tells him that he's Nick Fury of S.H.I.E.L.D. Fury then goes on to tell Stark that he's not the only superhero in the world, and he tells Stark that he's here to discuss the Avengers Initiative.
So there you have it. Misdirection and innuendo aside, Samuel L. Jackson is in Iron Man, and his appearance does set up Marvel's Avengers movie.
Iron Man opens everywhere May 2, 2008!