I loved Hulk smashing Loki. It was awesome. I may have gasped and said, "No! Not Phil!" in loud whisper voice.

I seriously want some smoking hot Black Widow/Hawkeye fic. Now.

As to comics... I did a quick search for Black Widow on torrentz.com yesterday and there appears to be an "Origins" series that I'm going to dl at some point. I also pulled her up on Wikipedia and it doesn't look like there's a lot of books that are just her or Hawkeye, but that they figure into other series. If you pull up their characters there you can get a lot of info on where to look for them.