I really enjoyed Rabbit Island and Even Ponygirls get the Blues by Aurelius, and enjoy most stories about training.

Although, I read this one story, and it just drives me crazy that I can't remember the name. It was almost Sci-fi (or off world), and this woman was captured, and as she travels to her new home with her Master, she is taught to accept his cum, wearing an o-gag. Then once she gets to her 'new home', she tries to project a younger slave by subjecting herself to an examination by a room of men....

Oh, the Association was fantastic as well....