MIT last week revealed plans to make its entire 1,800-course curriculum available online by year's end. The university has made the contents of some courses available on the Web since 2002. Some 1.5 million independent learners log on to the MIT OpenCourseWare site each month, and more than 120 other universities have established similar sites.

Who are MIT's independent learners? One MIT calculation found that 17% are educators at other schools, 32% are students elsewhere, and 49% are self-learners. About 40% of MIT alumni use the site, says Steve Carson, the program's director. "Usually they take courses they didn't have time for while they were students here," he says. Courses are free; no course credit is granted.

Other learners come from outside the United States, from Antarctica to Darfur. The highest domestic traffic comes from leading high-tech states Massachusetts and California, Carson says.

The OCW Consortium of universities with similar offerings includes Harvard Law School, Johns Hopkins Bloomberg School of Public Health, Michigan State University, Tufts University, University of Notre Dame, University of California at Irvine, and Utah Valley State College.