Donald Marron is preparing a list of the 50 most important economic ideas of the past century for a book publisher. He currently has over 60 ideas, but some are older (Marxism?) and the list is not complete. A few commenters have offered suggestions, but you should check it out and see if you have any ideas for improvement.
Perhaps he is missing something about economic sociology, or economic imperialism if you prefer? By this I mean the Becker, Murphy, Freakonomics style work that applies economic principles to every other social science, starting with Becker's work on marriage. Economic sociology is broader than that of course, but perhaps that would be one place to start.
What about science, technology and information economics? How well are those covered by his list? Thoughts?
All told though, he's done a great job. It's a great study guide for anyone looking for the major ideas of the discipline.