Sweet Chastity

Sweet Chastity is home to quite a bit of fiction, much of it dealing with chastity devices and body modification, much of it devoted to MTF transgender stories.

This is the home of the original Chasti-Permalock series and other stuff, some of which goes a bit too far for my taste, but you may enjoy it. There is a lot of permanent modification, some of it nonconsensual.
Permanent chastity is not part of my fantasy; I like the idea that the built-up tension will eventually be released in a super climax. Not all of the stories have that flaw, and even among the ones that do, there is some pretty good stuff.