How to Learn Something for Nothing

Thousands of pieces of free educational material — videos and podcasts of lectures, syllabuses, entire textbooks — have been posted in the name of the open courseware movement. But how to make sense of it all? Businesses, social entrepreneurs and "edupunks," envisioning a tuition-free world untethered by classrooms, have created Web sites to help navigate the mind-boggling volume of content. Some sites tweak traditional pedagogy; others aggregate, Hulu-style.

Academic Earth

Richard Ludlow started the nonprofit Academic Earth two years ago after M.I.T.'s OpenCourseWare helped him pass linear algebra as a Yale undergraduate. His site offers the courses of 10 elite universities — 130 full courses and more than 3,500 video lectures. Viewers can turn the tables on professors and grade courses. Other guidance includes "Editor's Picks" and "Playlists," lectures selected around a theme like "First Day of Freshman Year" and "You Are What You Eat."

Connexions

Connexions, started at Rice University 10 years ago, debundles education for the D.I.Y. learner. Anyone can write a "module," the term for instructional material that can be a single sentence or 1,000 pages. Connexions hosts more than 16,000 modules that make up almost 1,000 "collections." A collection might be, say, an algebra textbook or statistics course.

The service generates 70 million to 80 million page views a month, according to its founder, Richard G. Baraniuk. Readers can contact module creators with feedback or, because these are not immutable textbooks, to suggest edits. "The whole idea is to grease the wheels to make content up to date and correct," Mr. Baraniuk says. Teachers, for instance, can re-work examples and exercises, then republish the textbook for their own students.

Look for a stamp of approval on modules — a vetting system called lenses — from users, companies, universities and associations.

OpenCourseWare Consortium

The consortium — representing 250 universities around the world, from Japan to Colombia – aims to advance the reach and depth of free educational resources. Its Web site brings together course materials and lectures in different languages. Each member has to post at least 10 full courses within the first two years of joining. There are now more than 13,000.

Open Culture

Daniel Colman is a curator of sorts. He sifts through the vast amount of free courses, movies and books offered online to find what he considers the very best in content and production value. Then he features them on Open Culture, the Web site he founded in 2006. It's a task in keeping with his mission as associate dean and director of Stanford's continuing education program.

At last count, the site had 2,700 audio and video lectures from more than 25 universities; 268 audio books; and 105 e-books. Dr. Colman says he looks for lectures that "take ideas and make them come to life." And so you can learn 37 languages on Open Culture, or stream Jane Austen audio books, Hitchcock films and a John Hopkins biology lecture.

ITunes U and YouTube.com/edu

These satellite sites allow user-friendly browsing of free audio and video files. Plenty of self-promotion and silly stuff is mixed in with material of substance. But the scope is impressive.

The iTunes U portal at Apple's iTunes store is perhaps the largest entry point into all of online higher education, with nearly 300,000 audio and video files compiled from more than 600 colleges and universities around the world. YouTube, which started last year, currently hosts about 300 colleges and universities, with 200 full courses and 60,000 videos.

Highlights for High School

Why pay for test prep? M.I.T. OpenCourseWare has culled introductory courses in physics, calculus and biology, along with problem sets and labs, to help students prep for the Advanced Placement exams. (Not to miss an opportunity, there’s a link to the admissions office.)

The site also gathers free online courses in subjects like media, chemistry and literature to give a taste of the college experience, as well as a potpourri of demonstrations that high school students might find intriguing, like how to build electronic toys or to remove unexploded land mines.