50 Shades of Gray was a twilight fanfiction, and apparently it was good enough to be publishable.
I've not read it, but I'm given to understand that it has more fucking in it than HPMOR.
Also, I'm under the impression that people read it out of curiosity because it's famous for having lots of fucking in it, but when they've read it they don't think it's actually that great. (I haven't read it either, and I'm not going to read it in the foreseeable future either.)
"The kind of classic fifties-era first-contact story that Jonathan Swift might have written, if Jonathan Swift had had a background in game theory."
-- (Hugo nominee) Peter Watts, "In Praise of Baby-Eating"
Three Worlds Collide is a story I wrote to illustrate some points on naturalistic metaethics and diverse other issues of rational conduct. It grew, as such things do, into a small novella. On publication, it proved widely popular and widely criticized. Be warned that the story, as it wrote itself, ended up containing some profanity and PG-13 content.
PDF version here.