I didn't notice any easter eggs and it sounds like there was a reason for that. Kevin Feige isn't a huge fan of them.
"I find that they're distracting. Joss finds that they're distracting. Frankly we want Avengers to work as its own movie, as a part one. If you keep saying 'Oh look, it's Janet Van Dyne!' everything collapses. I took out some Easter Eggs in Thor because they were getting too [involved]. Selvig would go 'I'll email Dr. Pym who knew a guy named Banner.' It was too much!
"When Tony Stark throws up the screens after Coulson gives him [the dossiers on the other Avengers], those are Easter Eggs for people who haven't seen the other movies. They're clips of Thor and The Incredible Hulk and Captain America on those screens. Those are the Easter Eggs."