Keep it coming dot net has a site that lets writers sell their work in small, bi-weekly installments. The work covers a variety of genres and levels of quality.
I haven't used it (and I don't plan to) but I know someone who has. He earned a tiny bit of money from it, had a handful of readers, and was forced to turn out his work on a regular basis to satisfy his "contract."
He wasn't enthusiastic about it, but he admitted to enjoying it a bit.
Anyway, have a look.