So you want to create an online class independent of a school

What’s the best service or tool for creating and hosting an online class by oneself?

A client asked me this question last week, and I really didn’t have a solid answer ready to hand, since most of my work to date has involved institutions. So I started asking around, bugging individuals and querying social media. The results fascinated me. They also appeared in different places, so I thought it might be useful to aggregate and share them here, in one spot.