Keep the blood pumping. Iron Man, Incredible Hulk, Thor, and Captain America will converge in The Avengers in 2011.
The scene in which you can see the shield is after Iron Man returns from Afghanistan after fighting with the Mark III red/gold armor for the very first time. Right after he fights the two F-22 fighter jets, it shows him back in his lab trying to remove his armor but having trouble. Right as Pepper Potts walks down into his lab and asks him “what is he doing?”, the shield can be seen sitting on one of his tables behind him in the lower left corner.
Tim Blake Nelson holding the Captain America serum. Nelson, by the way, is playing Samuel Sterns in his still human form. In the comics, Gamma radiation turns Sterns into the Hulk villain The Leader. Sequel set up for Incredible Hulk part 2? You bet.
Next in line .................................... :P