You can post original fiction on
www.FictionPress.com (a sister site to FanFiction.net). Although kinky stories are in the minority there, I know some spanky fiction and other erotica have been posted on the site. You'd have to figure out though which genre to classify it under so you can attract readers who would enjoy this story. I know Lawrence Kinden from the LSF has stories posted there, mainly under "General" or "Romance." You can use the Search feature on the site, entering 'kinky' key words which might help you find other similarly-themed stories to yours to see how they're classified.
Another option, of course, is to create a personal blog on
www.wordpress.com and post your stories there. But that would only attract an audience whom you've given the blog address to, not the general reading public.