There's a really good one that I very much enjoyed called "The Secret Life of Hogwarts Heads" by Just-Like-Ginny. Now, it's 20K words long so it's going to take patience to read through all of it, but trust me, it's worth it.
Anything by Josephinee. Just go google the name and you'll get the link to her fanfiction. I recommend starting with Chronicles and Paramnesia. All her stories (except one)are complete, so no waiting for updates.