I recently came across an HP AU Fanfic, Prince of the Dark Kingdom. It is a huge story, over a million words and is, I think, complete (haven't finished it yet).
I mention it here because it is very good with particularly good renditions of some of J K Rowlings nastier characters, Snape and Voldemort in particular. In my opinion these two characters, who are central to the story, are much fuller and far more well rounded characters than Rowling herself penned
http://www.fanfictio...he-Dark-Kingdom
PS It is not complete after all, but the dates seem to indicate it is still in progress.
PPS A new chapter has been posted so it is still in progress.