From The Open University in the UK, OpenLearn has free articles, audiovisual materials and study units on a wide range of subjects.
The many free online courses available are based on courses that have been taught at the Massachusetts Institute of Technology in past semesters.
Another Open CourseWare resource. This site includes the MIT OpenCourseWare programs, along with courses developed through several other universities.
Open Educational Resources: Textbooks
This is a collection of textbooks that have been licensed with Creative Commons copyrights, so access is free and open.
The Open Learning Resources Network website has an extensive collection of free, online resources for personal educational development. The organization is based in India, but the links are valuable for anyone interested in broadening their knowledge online.