Thor: he was trying to pull Mjolnir out of the ground with his pick-up. The Avengers: he was being interviewed at the end and said something along the lines of "superheros in New York? Give me a break." He also appears in the Spider-Man ride at Universal Studios.
I just wanna movie where Stan Lee just becomes like a main character, and he just gathers all the avengers and says, "I've been watching you for years." And they all just gape and Tony is just staring at him and Stan says, "You too Tony Stank."