A few ideas for the yet-to-be-cast Avengers...
Patrick Wilson as Hank Pym
Having already had experience with the geeky-yet-heroic Night Owl in Watchmen, I feel like Wilson is a good pick here. He has the right vibe for Tony Stark's equally as brilliant, but nowhere near as charming, teammate.
Amy Acker as Wasp
On Angel alone, she showed that she can play caring, brave, quirky, brilliant, badass, etc. Pretty much whatever you need in a supporting actress. She's just a few years younger than Wilson, I believe, so would be a good match for his wife.
Paul Bettany as Ultron/Vison
This is kind of cheating and has already been done, but I feel this really works. Let's say Stark helps Pym with the creation of Ultron. It would be conceivable that they would use the same basic voice that he has already used for Jarvis. Then, in true Godly fashion, Ultron creates Vision "in his image." Vision would actually allow for Bettany to get physically into the role, even if it is just motion capture.
Brandon Routh as Wonder Man
Lots of people on here have been searching for Routh's next shot at a superhero since he won't get a Superman follow-up. I think Wonder Man could be that shot. He definitely has the looks/build for it.
