There is an entire Stories area here with user-written stories.

If you dont know about ASSTR (Adult Sex Story Text Repository) it is a totally free site with years of hot stories that have been passed around Usenet.

For non-fiction, I used to have a good book something like:"Spanking: how to get wonderful people to do naughty things to you."

If you are into eBooks, here are some titles of some top-rated books you can get from Fictionwise or the bdsm ebook sites. I made a list as there was a 40% off sale last weekend:

RAVISHED BY THE PIRATES
THE LEARNING COMMUNE (Hector McIntyre)
JULIE'S ABDUCTION NIGHTMARE (W.L. Dowd)
CASTLE OF PLEASURE AND PAIN (Powerone)
KIDNAPPED TO BE A WHORE (Powerone)
GIRL HUNTERS (Powerone)
A FAMILY - BOUND, SOLD AND TORTURED (W.L. Dowd)
ENSLAVED: A New Society (Powerone)
HELL HOSPITAL (Powerone)
DEVIL`S SLUTS (Powerone)
THE CHASTENER (Hector McIntyre)
THE SOCIETY - Book 1 (DrkFetyshNyghts)
ABUSE OF POWER (Dan Bruce)
A FAMILY - BOUND, SOLD AND TORTURED (W.L. Dowd)
PUNISHMENT ROOMS (Hector McIntyre)
WAR VICTIMS (Powerone)

Hope this helps.