Aha, I ran across this rundown recently. It might help.

Honestly, IMO the Marvel movieverse is different enough that knowing the comics is not necessarily an advantage. Widow was in Iron Man II, and Hawkeye is briefly in Thor (you do get a nice window into his personality there, if you haven't seen it yet).

There is a new Hawkeye comic going on now by Matt Fraction that's a fairly new take on the character (and more in keeping with the movies, as far as I can tell) that has been well-loved. The first trade is due out in March. The Brubaker Captain America issues coffeeandink talk about are also very good (at least the ones I've read).

Oh, and EDIT: Marjorie Liu's Black Window is indeed supposed to be good, I've liked the excerpts I've seen and I love Liu.

Edited at 2013-01-08 03:45 am (UTC)

I would probably say unless u really want to delve into the Marvel universe its going to be hard to pin point one thing to read to learn more about their relationship but i heard they're coming out with a movie more based around the two of them.