There is lots of web-based and text archives of stories.
Do a search for ASSTR (Adult Sex Story Text Repository). About 15 years of sex stories, all free in text format.
If you want some of the Beeline, Greenleaf etc. novels in text format, try:
http://neatopotato.net/xnovel/
Hundreds of books have been hand-typed to create the collection. (Saddly this means there are some typos but most of the stories are intact).
And dont forget Literotica - Lots of great stories.
Hope this helps.