1. The best name from the Harry Potter world is Miraphora Mina. No, she's not a character, she created some of the props.
2. EW has a great collection of photos of Potter props and sets.
3. EW also has a short article by Chris Columbus in which he he blames the lousiness of the first two movies on the kids' inability to act:
The first film was shot in an almost documentary style because the actors were so untrained and raw . . . . That's why the first film is an exercise in rapid editing . . . . By the time we got to Prisoner of Azkaban, Dan, Rupert, and Emma were able to perform an entire scene in one long, continuous take.Hmm, I can think of a different reason why number 3 is so good, and why 1, 2, and 4 are so bad.
4. Finally, there's lots of great Potter concept art at Rob Bliss's site.