Freely available filthy prose
» Erotica
You may have never heard of Usenet, older than the web people use it to share many things. Including the porn they've written. The quality various considerably. Good, lame, lousy. But just as some people prefer to look at naked photos of ordinary people instead of airbrushed models you may like homebrew dirty stories. Or you may have a special fetish that isn't easily or adequately sated.
You can:
Read the groups via Google.
Check the Alt Sex Stories Text Repository.
Or if you'd rather keep them on your PC for later reading and rereading you can:
Setup a newsreader.
Moderated groups are best since they keep the spam out. There's a FAQ.