CourseTalk is a nice search engine for MOOCs

Massive Open Online Courses – MOOCS

Coursera
edX
France Université Numérique
Udacity
Udemy
CodeAcademy
OpenAcademy

FutureLearn

Complexity Explorer (Mathematics for Complex Systems)

About Massive Open Online Course, Wikipedia

Extension Schools

Harvard Extension School – can earn you credit (tuition $1250 ~ $2200)
Stanford Online