Coursera, Udacity, MIT Open Courseware, and other such sites are useful to me because they decouple the desire to learn college-level material from the expense and regulations of earning (another) diploma. The latter isn't compelling to me today, but the former certainly is. I've now taken three Coursera courses: Functional Programming Principles in Scala, Social Network Analysis, and Coding the Matrix: Linear Algebra Through Computer Science Applications. I also tried to take Calculus: Singl...