a couple classics, imo:
http://img301.imageshack.us/my.php?image=avengers17710sk4.jpg
http://img264.imageshack.us/my.php?image=avengers165180001ut3.jpg
i can't really overstate the impact those 2 arcs had on me in terms of my love of comics. the original korvac arc and the original nefaria arc. those old avengers issues are STILL among the best i've ever read. i've pretty much loved thor ever since . . .