Good answer for you: do a google search of the usenet sex story newsgroups.
In the Newsgroup box, put in either alt.sex.stories, or alt.sex.stories.moderated.
This should give you tens of thousands of sex stories. If you wanted to, you could narrow down the search by searching for words of particular interest, in case you want to find a sex story about Oprah Winfrey, or "teen lesbians", or "naked penguins", or whatever.
(And sure, you probably thought I was kidding about those topics, but I just tried a search, newsgroup alt.sex.stories, for "oprah", there were 298 hits. Although I think they were probably just stories which contained the word Oprah, and not stories about her)