2008/9 Wikipedia Selection for schools - this 2008/9 Wikipedia DVD Selection is a free, hand-checked, non-commercial selection from Wikipedia, targeted around the UK National Curriculum and useful for much of the English speaking world. It has about 5500 articles (as much as can be fitted on a DVD with good size images) and is about the size of a twenty volume encyclopaedia (34,000 images and 20 million words). 

Academic Earth - Free online lectures from some of the world's top universities 

Florida Virtual Library - Florida Virtual School's online library. offers plenty of great online resources

MIT Highlights for High School-"Highlights for High School features MIT OpenCourseWare materials that are most useful for high school students and teachers."

MIT Open Courseware-"Free lecture notes, exams, and videos from MIT. No registration required."

Open Source Text Books-Free online textbooks.

Research Channel- Online educational video library

UChannel-"A collection of public affairs lectures, panels and events from academic institutions all over the world

-- for you to view, listen to, stream or download."

Annenberg Teacher Media Resources-browseable media programs, sign-up required

Open Learn "The OpenLearn website gives free access to Open University course materials. This is the LearningSpace, where you'll find hundreds of free study units, each with a discussion forum"