Ng says the forums have made the ability to educate and engage thousands of students feasible.
"If you want to learn something, sitting at home watching YouTube videos is kind of a lonely experience," he notes. "Having a community of students working on the material together—that helps students learn."
2. Udacity: Former Stanford professor Sebastian Thrun cofounded this online learning community in January 2012 after also teaching a free online Stanford course in fall 2011 that enrolled roughly 160,000 students.
"That made me wake up and think about education in general and realize that we have a system that serves a small number of people, and it's very exclusive and very expensive and nonscalable," he says.
Udacity, which currently offers computer science courses, relies less on video lectures and enables students to do more work through online quizzes and exercises, Thrun notes.
Udacity also depends on a vibrant community of peer learners to ask and answer questions in the forums, he says. "In fact, there are many instances when a student's quality of answer to a question exceeds my own quality of answer."
While Udacity's goal is to educate as many people as possible, the organization also focuses on job placement. Working with companies such as Google and Facebook, Thrun notes that Udacity has been able to "place about a half dozen students into jobs."
[Read how online degrees don't impede the job search.]
3. Udemy: Offering courses such as "How to Create an Awesome Demo Video for Your Business," Udemy has branded itself by offering many courses that would not typically be found on a college campus.
"You go to Udemy because there's a specific thing you want to learn," says Richard Komaiko, who took the demo video course to improve the visibility of his business, AttorneyFee.com, a site for comparing lawyer costs. "The type of stuff that can't be found in a real university—that's what Udemy excels at."
Founded in May 2010, Udemy provides anyone with an Internet connection the opportunity to teach or learn online, says cofounder Bali, who leveraged online resources while growing up in southeast Turkey.
While some courses charge a fee, Bali notes that the majority of classes are free—including "The Faculty Project" courses, which showcase content from university professors—and focus on providing marketable skills to users.
"You cannot expect to just go to college and have it convert to the best job opportunity," he notes. "You need more unique skills. You have to improve your credibility."
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