A - General works

Annenberg Media
Free video on demand. Free sign-up required. Browse by discipline and grade level (includes college/adult). Topics include history, literature, maths, arts, languages, and more. Targeted toward educators, so there is also some pedagogical stuff.
Archive.org’s Open Educational Resources
Welcome to the Archive’s library of Open Educational Resources and university lectures. This library contains hundreds of free courses, video lectures, and supplemental materials from universities in the United States and China. Many of these lectures are available for download.
Carnegie Mellon Open Learning Initiative
“Open & Free courses are freely available online courses and course materials that enact instruction for an entire course in an online format.”
Connexions
View, create, share learning modules on many topics.
Frontline (PBS)
“Selected FRONTLINE programs can be watched here in full - QuickTime and Windows Media formats.”
MIT Open Courseware Audio/Video Courses
Directory (organized by department) of courses containing substantial video and/or audio content. I love MIT Open Courseware overall, just for the reading lists.
Online Books @ University of Pennsylvania
A listing of over 30,000 free books on the Web, old to new. Browse by LCC, even.
OpenUW
A series of free courses from University of Washington
Research at Chicago
Video interviews with researchers at University of Chicago. Browse by topic. Can also download mp3.
Stanford on iTunes
Courses, lectures, interviews. Free. But I refuse to use iTunes.
Textbook Revolution
“TBR’s mission is to drive the adoption of free textbooks by teachers and professors.”
UC Berkeley Webcasts
Webcasts and podcasts. Many topics. Courses and speakers.
Utah State University
Listing of free online courses.
WGBH Forum Network
Live and Archived Webcasts of Free Public Lectures
in Partnership with Boston’s Leading Cultural and Educational Organizations. Many topics. Some lectures in series. Podcasts and downloads available.