I stumbled upon AnthologyBuilder the other day. They hold an archive of stories and the buyer can “build their own anthology”. I haven’t chosen which stories I want yet, but if you want to read about someone else’s experience with it, you can do so here. It sounds like the final product is quite professional.
Also, I decided to submit my story, “The End of the Road” (previously published in Not One of Us). It was accepted and now anyone who might want to read it can include it in their own custom anthology.