* Wiki books * Wikiversity * WikiEducator - dedicated to building a complete education curriculum by 2015 * ck12 - free, flexible textbooks for the whole American educational syllabus * Disqo * Khan Academy - a series of tutorial videos, mostly of science and maths, explaining concepts very well. * MIT's YouTube channel - Includes entire lecture series. The one on linear algebra in damn good. * Open Yale Courses * Stanford's YouTube channel * United Nations University OpenCourseWare * John Hopkins OpenCourseWare * eToys - free and open-source software that teaches ideas in innovative ways. For kids * Open University's Open Learn * P2P university] * Connexions - Open educational content in hundreds of subjects. * List of educational video websites on Wikipedia * Open Culture - list online courses * Wolfram Demonstrations Project - A compilation of pretty interactive visualizations of hundreds of phenomena in science, mathematics, music and other areas. Enjoy!