I've only been reading fanfic since May and I can't remember for the LIFE of me what I read first. I'm sure it was on LJ, because that's where I first found QaF fandom people.
I do have a few that stand out for me as the best...will that do?
In Cars, by severina2001 (Everything about this fic makes me smile, I practically have passages memorized, I've read it that much)
Divergence, by ragingpixie (This might be my fav of all time)
Plans, by xie_xie_xie (This one is post-513 canon in my mind)