If you’re serious about world building, this one might be something for you: The California State University is/was offering a course in World Building. The course is offered both on-campus and as a distance learning course. It focuses on realistic, scientific world-building. I am not sure if the course is still actively offered; the Open University does not seem to list it. I’m actually interested in this course, but unfortunately the professor who taught it does not reply to email at the moment. A pity.
Update: Also seems the Cal State site doesn’t respond anymore. Too bad. Does anybdoy know of a similar offer?