Ran a course. Sold a screencast. (Over $10k within 2 months for both.) A little busy to go into details right now but there have been lots of posts with similar case studies on HN - one of the better ones was http://sachagreif.com/lessons-learned-from-an-ebook-launch/
I've always had a passion for publishing and have tended to build up news sites, blogs, and now e-mail newsletters in the areas I find interesting. So prior to both the course and my screencast, I already had a five figure audience on the right topics and a huge home advantage.
I'll note, however, that this is by no means required, and people in my position frequently become friendly with others with such projects and help them out.