<a href='http://www.equestriadaily.com/2011/06/story-silent-ponyville.html' target='_blank' rel='nofollow'>Silent Ponyville</a> has updated with multiple continuations as well as spin offs.
I've read a good number of Silent Hill fanfics and I've read a good number of My Little Pony: Friendship Is Magic fanfics. The stories featured within that thread are not only decent, but clever and well developed as well (the newest ones can't be called 'well developed' as they're still developing, but are off to decent starts) with only the occasional spelling error.
A few prominent OCs are inevitable for the sake of a few of the stories, but all in all, I consider them well above average.
<a href='http://www.equestriadaily.com/2011/09/story-my-little-hangover.html' target='_blank' rel='nofollow'>My Little Hangover</a> is up to chapter 5 and has a number of amusing bits within. I couldn't help but think that, even if you dislike her, Katie Perry's "TGIF" song should be playing during Chapter 2.
<a href='http://www.equestriadaily.com/2011/06/story-and-then-then-she-exploded-twice.html' target='_blank' rel='nofollow'>And Then She Exploded! TWICE!</a> - A fanfic wherein Rainbow Dash reads another fanfic about her, and decides to make her OWN fanfic.
She then goes looking for praise. Why, that sounds like many other newbie fanfic writers! Surely, Rainbow Dash won't fall to those pit traps of early fanfic writing, right?
Right?
Probably made to nitpick others. I'm mostly noting it because I was amused by the concept.
<a href='http://www.equestriadaily.com/2011/02/story-everypony-loves-dash.html' target='_blank' rel='nofollow'>Everyone Loves Rainbow Dash</a> - Rainbow Dash wakes up one morning to find that everyone in Ponyville seems to have the hots for her. My only real complaint towards this story is that it could've been condensed down to one long fanfic rather than the 16 or so 3 page chapters it is.
Edit: <a href='http://www.equestriadaily.com/2011/09/story-dairies-of-equestrian-overlord.html' target='_blank' rel='nofollow'>Diaries of an Equestrian Overlord</a>. Found it today. It's 172 pages, fun, disturbing and, strangely, heart-warming. Ya silly little peanuts.