Another story site:

http://storiesonline.net/user/p_legal.html

As far as www.asstr.org/ is concerned its a repository of stories that have been posted to Alt.Sex.stories.*

You can search the newsgroups themselves through Google to find the most current posted stories or installments of a series in "Google Groups". (Google groups is the discussion or text only groups on Usenet. There are no binary groups.)

http://groups.google.com/groups/dir?lnk=nhpsfg&hl=en&q=alt.sex.stories&qt_s=Search+for+a+group

I recommend alt.sex.stories.moderated since it has the least amount of spam and the most actual content out of the groups although you do occasionally find a gem in the other groups if you shift through the fodder long enough or just get lucky.