I've read quite a bit of fan fiction. I've also written a little bit. I was also once the subject of a fanfic (tee hee). But even when I searched Google on a whim (I do a lot of whim Googling), I didn't expect to find this. It's a directory of fan fiction.
(For the uninformed, fan fiction is a story written by a fan of a particular TV show, movie, book, etc.; placing those characters in a different situation or plot.)
Although this site certainly doesn't have everything, it has a lot. There are 206,181 fanfics based on Harry Potter. There are 13 based on Good Night Mr. Tom, that dumb WWII book I had to read in 8th grade.
I was sad to find that among the 206,181 Harry Potter fanfics, the one I had read, The Naked Quidditch Match, an epistolary, was not listed. See, I hadn't finished reading it because it was still being written. Or, the author had taken a break. But apparently now it's finished, and I can go find out what happened.