http://clitoridesawards.org/

The Clitorides Awards are an award for online authors who write sex stories. It originally ran from 1999 to 2006 and is being brought back again for stories of 2013.

Most of the writers post their stories on at least one of the following sites:

www.literotica.com/stories/ (scroll down some for the stories)

www.storiesonline.net (SOL requires you to join to access their library but their free membership is quite good. You are limited to 16 stories a day and can't use the sites advanced tools)

http://www.asstr.org/

http://www.bdsmlibrary.com/stories/

http://www.understories.com/

bump cause someone else must read porn too.

The Story of O is such a perfect work of written porn, that it is hardly worth writing more...

Most other great written porn is individual passages in non-porn: what differentiates writing from Hollywood, is that hardcore sex is often present in "mainstream" novels, but not mainstream movies. Mostly I suspect because the bluenosed morality police is illiterate, but very much capable of looking at moving or still pictures.