By Katrina Schwartz

As the current generation of college graduates wrangles with an unprecedented amount of debt, a sea change is underway in higher education. More and more elite universities are offering free online courses that might characterize the next iteration of the college experience for the forthcoming generation of students.

Will students be able to receive the equivalent of a bachelors degree for free? How will brick-and-mortar institutions be used in the future? Will academic rigor suffer? How will credentials or tuition apply to those who come to campus and those who complete courses online?

At the moment, students of these online courses receive certificates of completion, but no university credit. But the movement is still in major flux as we speak, as day by day, yet another development in free online education is announced. What started 11 years ago with MIT's OpenCourseWare -- the syllabi, lecture notes, problem sets and solutions, exams, reading lists, and event video lectures from more than 2,000 MIT courses -- has amassed into an explosive movement that's compelling venerable institutions to reconfigure their education platform to an online audience.

Last fall, a group of Stanford professors decided to offer a few courses online free of charge and were overwhelmed when hundreds of thousands of students signed up for their courses. That experiment has spawned the growth of similar endeavors. Here's a guide to some of the newest free education sites and what they offer, with the big caveat that this will soon change, as more institutions come aboard.

COURSERA. Coursera is an interactive online learning system that offers free courses from Princeton, Stanford, University of California, Berkeley, University of Michigan—Ann Arbor and University of Pennsylvania. Their courses span the range from humanities, to social science, computer science, business, biology, medicine and mathematics. Andrew Ng, one of the Stanford professors whose class drew an astounding 100,000 students, and his new business partner, Daphne Koller, announced that they received $16 million in investment capitol from two prominent Silicon Valley firms to launch the project. Students will have access to lectures, interactive elements like quiz questions interspersed throughout lectures to help students recall and retain information, and peer-grading for homework, essays and tests. They plan to use crowd-sourcing algorithms to help ensure accuracy in peer grading, a move that will also help professors manage such large-scale classes. What's more, Coursera’s partner institutions will use the online learning platform to enhance in-class teaching. Based on a Department of Education study that shows online learning can be as effective as classroom learning, the participating universities will offer a mixture of interactive and static learning to explore the best way for students to retain the information. CERTIFICATION: As with the popular Stanford courses, students will not get academic credit from the participating institutions, but will receive a certificate of completion from the professor.

MITx --> edX. MIT took its OpenCourseWare platform to the next level with MITx, which offers full professor-taught courses online (not just class materials), but after just one course this spring (Circuits and Electronics), MITx entered an agreement with Harvard, and is now part of edX. The two universities will use the MITx platform to bring in a wider array of classes to the site. What's key here is the software for the platform is open-source, so other universities can use it too. The more universities add content, the more compelling a choice edX becomes amidst the growing number of offerings. Both schools have invested heavily in the project -- each gave $30 million to a non-profit organization that they will co-manage. Edx will feature video lectures, embedded quizzes, interactive learning, online labs, and a lot of peer interaction. CERTIFICATION: Certificates of mastery will be given to students who demonstrate knowledge of course material.

UDACITY. Sebastian Thrun, one of the professors who offered the first set of free online Stanford classes last year, which drew 160,000 registrants (22,000 finished the class), left a tenured position at the university to start Udacity, which focuses on computer science. Thrun taught an online artificial intelligence course for free at Stanford last fall with Dr. Peter Norvig, another artificial intelligence expert. Their course drew 160,000 students, with 22,000 students finishing the class. That inspired Thrun to start Udacity, which pulls in outside experts like Reddit co-founder Steve Huffman, to teach courses. They do not operate under the auspices of a university, although some of their guest-lecturers do teach at other universities. Their course offerings are aimed at practical computer science skills, like how to build an app or search engine. CERTIFICATION: Students receive a certificate of completion at the end of the course signed by the instructor.