I think a lot of HP fandom types can remember their first discovery of Cassandra Claire's stories in the same way that people remember where they were when they heard that man first walked on the moon, or when famous people died. Me, I found Cassie's A Season In Hell first off, early on in my discovery of HP fanfiction, back in late 2002. I remember I was on vacation and in a hotel, and read the thing cross-legged on my hotel bed, using dial-up and a hotel bible for a mouse wrist rest. I was writing my first HP fanfiction at the time--Other Chambers, Darker Secrets--and was poleaxed. Literally (as in, well, literally fell over, not literally hit with a poleaxe. Heh). Lay there across the garish hotel bedspread, breathing shallowly, wondering why on earth anyone should bother trying to write anything else after that. And I read Draco Dormiens the next day, and had to stop writing OC, DS for three days because I had to write fanfiction for her fanfiction before I could go on (that was Because of Who You Are--total fluff, but I was in LOVE, man). I'll never forget how sweet and gracious she was when I sent that story to her, asking her if she'd mind if I tried to archive it on restrictedsection.org.
Draco Dormiens, Draco Sinister, and Draco Veritas are, someone's calculated, almost one million words of fanfiction. The stories and characters within them mean almost as much to me as Rowling's series itself.
There's a big fat ache in the center of my chest for the end of this one. I'm sure I'll be having a cry soon.
*thegraybook is letting us know that at some future date her fanfiction may/will be removed from web archives, so those of you who want to read it should save copies now. Pdf files of the three parts of the Draco Trilogy (with pictures!) are available at the bottom of the DV epilogues page here.