Editors' note, August 21, 2012: Updated to include information on EdX.
Seeking out higher education is certainly admirable, but it can also be a serious drain on the pocketbook. If you don't need the letters after your name, there are many terrific, free online sites that offer coursework on everything from algebra to zoology. Here are some of the best:
EdX. New for fall 2012, EdX is a joint venture of MIT and Harvard and offers what is currently a limited number of ambitious courses. UC Berkeley has signed on to provide content, and if the experiment succeeds, we can expect more top schools to add their expertise to the site.
MIT OpenCourseWare. Among the very earliest adopters of free, open access to educational resources, MIT has been offering its materials to the public for nearly 10 years. Almost all MIT course content is available online, and while, like most of these resources, you don't get a degree or direct access to instructors, the quality of written and multimedia materials is first-rate.
Coursera. This for-profit organization does offer its coursework for free, and it's good stuff. Classes last from 4 to 12 weeks and come from academic powerhouses like Penn, Stanford, Berkeley, Michigan, and Princeton. Though it's somewhat heavy on computer science classes, it does offer world history, economics, and more.
Academic Earth. Styling itself as an academic version of Hulu, this site collects freely available lectures and coursework from many different sources. Though it's not as narrowly focused as some sites, it does offer something for everyone and is well worth checking out. Note: It was recently acquired by Ampush Media, but hasn't seemed to change the availability of its materials.
iTunes U. It's not all free, but there's a vast amount of course materials available using the iTunes U app. Many schools use the app to build content for their students, and while most of them require a secure logon, some make some materials freely available to the public. Download the free app and browse around.
Khan Academy. Though it's geared toward K-12 students, the Khan Academy videos and problems sets are rightly beloved by learners of all ages. Much of the content deals with math and science, but the site has branched out into economics and the humanities as well. It's well worth a look for anyone seeking a refresher or wanting to tackle a subject for the first time.
Textbook Revolution. This site is run by students and is essentially a catalog of free online textbooks and course materials, including some mentioned above and many others that aren't. It's pretty bare-bones, but if you're looking for a good free textbook or learning plan, this is the place to go.