Many years back (more than 10) I came across a PDF for Harry Potter and The Order Of Phoenix. It had a completely different story line. If I remember correctly, in the first chapter Harry was meddling around in the garden thinking about his own physical growth and over the course of the book there was a love angle between him and Hermione. Some portion that I can recollect from the first chapter is about a snake Harry encounters in the garden and the snake is not in a really good shape and Harry takes care of it. Rest of the year in the school was completely different too, Sirius doesn't die as per the story and it's a gradual build up to his and Hermione's relationship.
I have never been able to find that PDF again.