What we learnt from Dumbledore's notes in Tales of Beedle the Bard, and I'm not talking about things related to the tales themselves, rather I'm talking about the things related to canon.
- Brutus Malfoy, an ancestor of Lucius Malfoy, was the editor of an anti-muggle periodical called Warlcoks at War around 1675
- Professor Herbert Beery was the Herbology teacher when Dumbeldore taught transfiguration at Hogwarts
- Professor Silvanus Kettleburn was the Care of Magical Creatures teacher at that time, and he had at least sixty-two probationary periods during his teaching career. His relationship with Armando Dippet was strained.
- There has been only one attempt at a play or pantomime at Hogwarts- The Fountain of Fair Fortune, when Dumbledore was Transfiguration teacher. He had to do the "special effects"
- Professor McGonagall became the headmistress after Dumbledore's death
- A warlock is a wizard of fierce appearance or a title of particular skill or achievement
- No witch has ever claimed to own the Elder Wand
I just thought it would be helpful. Anything else? I didn't include books like Hairy Snout, Human Heart, authors, magical laws and stuff like that.
Professor McGonagall is generally agreed to be the Headmistress after Hogwarts, but not every one agreed to this- we have proof now.
Also- is this book, and the other two companion books considered canon?