SPOILER: A scene appears after the closing credits: Tony Stark arrives home to find SHIELD director Nick Fury waiting for him so that they can discuss the Avengers Initiative. This leads into The Avengers (2012) (a superhero team of which Iron Man is a founding member).
This is Marvel Studio's first self-produced film (and the first film to set up the Marvel Cinematic Universe), so the Marvel logo is slightly adjusted: it fully appears, and then is accompanied by the title "Marvel Studios."
Part of the closing credits are seen against computer-graphic renders of armoured suits. One of the renders is an armour with a Gatling gun attached - the War Machine suit, which would appear in Iron Man 2 (2010).