MIT OpenCourseWare
MIT describes its OpenCourseWare site as "a free and open educational resource for faculty, students, and self-learners around the world." We describe it as "the closest thing to a free MIT education."
With a Master Course List of over 500 courses from five of MIT's schools (including the Sloan School of Management), MIT's OpenCourseWare provides a treasure trove of reading material. For communication professionals, we recommend the notes from two classes in particular:
15.279 Management Communication for Undergraduates 15.280 Communication for Managers