“Taking a course online, by yourself, is not the same as being in a classroom with a professor who can respond to you, present different viewpoints and push you to work a problem,” Professor Neem said. “There’s lots of porn and religion online, but people still have relationships and get married, and go to church and talk to a minister.”

But Anya Kamenetz, whose 2010 book, “DIY U: Edupunks, Edupreneurs and the Coming Transformation of Higher Education,” tracks the new wave of Web-based education efforts, says the new institutions will only continue to improve and expand. “For some people, it will mean going from a good education to a great one,” she said. “For others, it will mean getting some kind of education, instead of nothing.”

The emerging menu of new offerings is startlingly varied, as are the institutions. One unaccredited nonprofit startup, University of the People, gives English-speaking high school graduates a chance to study business or computers free, with volunteer teachers. There are also budding joint ventures between brick-and-mortar campuses and online entities, like Ivy Bridge College — a collaboration between Tiffin University, a nonprofit school in Ohio, and Altius Education, a commercial business, offering two-year online degrees transferrable to dozens of partner four-year colleges. And there are grass-roots nonprofits like Peer 2 Peer University, where people start study groups on topics as diverse as JavaScript and Baroque art.

Nationwide, almost three quarters of college students attend public institutions, and commercial career colleges like the University of Phoenix and Kaplan now make up almost as much of the remaining quarter as traditional nonprofit private universities like Stanford or Duke. Many of the emerging models are far cheaper than the publicly traded career colleges, some of which have come under scrutiny over the last year for leaving students with mountains of debt and credentials of little value.

Most are still new and very small, making it hard to locate students who have used them, other than those referred by the businesses themselves.

And it is too soon to know which will take off, or what might come along to overtake them.

“I’m just waiting for a Wikipedia University, with high-quality, online, open-source courses provided by a variety of different people,” said Richard Vedder, an Ohio University economics professor who directs the Center for College Affordability and Productivity. “Or the moment when someone like Bill Gates creates Superstar University, finding the best professors for the 200 courses that a good liberal arts college offers, and paying them $25,000 each to put their classes online.”