Following the lead of the Massachusetts Institute of Technology and other highly competitive schools, more institutions are posting online everything from lecture notes to sample tests, and even making audio and video files of actual lectures publicly available. The sites attract anywhere from thousands to more than one million unique visitors each month.

MIT's pioneering "OpenCourseWare" program, which was launched in 2003, posts the syllabus and class notes for more than 1,500 courses online for anyone who wants them.

The University of Notre Dame in South Bend, Ind., offers from Introduction to Philosophy to African American History, and including everything from class plans, links to required readings, lecture notes and homework assignments. .

YaleUniversity produces digital videos of undergraduate lecture classes and makes them available to the public.

Some smaller liberal-arts schools are following suit. Bryn Mawr College, a women's school in Pennsylvania has selected course materials to post online for the public.

Some schools that follow the MIT model are focused on making available as many course materials as possible -- including class plans, lecture notes, lists of reading materials and even homework. Other schools, including University of California, Berkeley, are simply making lectures available through audio and video files. In MIT's Introduction to Modeling and Simulation, a science and engineering class, Web surfers can browse through assignments and sample quizzes, as well as suggested project ideas. As with other MIT courses, the syllabus is posted -- so you can see the structure of the course and what text and other reading materials are used -- but only some lecture notes are available.

Five prestigious US universities offer free online courses. Check this out at coursera.org

Largest On-Line Schools