I loved 'Classical Sociological Theory'. It introduces the ideas of 8 'sociological' thinkers from Bernard Mandeville to Norbert Elias. The course uses the medium of a MOOC by providing insightful pictures and the course references interesting source material.
The course that brings me the most in terms of concepts I keep coming back to in everyday live is 'Introduction to Psychology': https://www.coursera.org/learn/introduction-psychology
I must confess I always find it quite hard to take psychology very serious, but this course does a good job at cutting to the bone of what psychology is about and refrains from making unfalsifiable statements.
EDIT: Almost forgot Astronomy: Exploring time and space: https://www.coursera.org/learn/astro. It comes with a very awesome free online book/website.