IMO, this is a very clear summary of major MOOCs available for us today. I have taken courses on all the above MOOC offerings and completed courses to varying

IMO, this is a very clear summary of major MOOCs available for us today. I have taken courses on all the above MOOC offerings and completed courses to varying degrees. For a Software professional, the rigor in increasing order is: Udemy, Udacity, Coursera and edX. Of course, this is a very high level generalization and depends on each course/professor.