First off- I've read every Harry Potter book 3+ times each, and have read the 3rd 8 times now. I have sen ever movie out hundreds of times, and I even visit a few Harry Potter fan sites, like Mugglenet.
That being said, I have thought long and hard towards their types, and with everything I know towards Harry Potter- this is what I have.
Harry Potter: ISFP
Harry is in the Griffyndor house, which in and of itself is an FP house- fighting for what they believe in. Harry is total non comformist, he avoids people, is very curious of things, likes to get cement evidence to put towards his theories, he isn't extremely logical, practical, or insightful, but acts spontaneously based on his emotions.
Ron: ESFP
Ron is definitely SP, no doubt about it, he likes getting assurance from people around him (E), he sticks up for Harry even if means getting in trouble or risking safety (F), he defends his family values (F) and he is a perfect match as best friends with Harry. He also lacks a little self confidence, which doesn't necesarily an ESFP thing..
Hermione: ISFJ -> INFJ
She is clearly a SJ at the beginning of the storyline especially with how stuck up and prudy she was. But as the story got more involved, she really sets aside his little miss rule follower character and starts providing for Harry and his overall goal, in which, you can say she is more like an INFJ. If it weren't for her, Harry would have never made it through the Triwizard tournament, as well as other things she's pulled Harry through. She is secretive, especially with the time turner in the third book, and she can often see events as they are unfolding. They gives off a motherly vibe to Harry- something clear of her INFJ, and she is the strength he needs throughout the book.
Dumbledore: INFJ
This is pretty much a given, as he is very wise, and is rarely lead the wrong way. His intellect is sharp, his mind weary and sharp. His wit is sharp, and he almost gives off a bit of a silly character. From the seventh book, we find out about Dumbledore's past- how smart and perfect he was as a kid, his need for adventure, and his interest in the Deathly Hallows- which one can infer is very INFJ-like. He is very sensative and cares deeply for Harry as an individual (Fi).
Hagrid: ISFJ
Hagrid is a teddy bear- admitt it. He is very sensative- as with Norbert the dragon from the first book. He doesn't fight for justice- yet stands up for Harry and his values even though it risks his status as a teacher. He is definitely SJ, though, as he doesn't see the plot too clearly throughout the book.
Draco Malfoy: He seems very ESTJ, maybe ESTP.
Draco is a tough one, even with study. He is surely an EST, as he is constantly aggitating Harry and looking for trouble and trying to get back at Harry. His roll in the 6th book may show an ESTP side to him, and how much of a struggle it was for him to fix the disappearing chair in the room of requirments. He sees his destiny as a death eater (even though he doesn't end up bad in the very end of the 7th), and is loyal to them.
Arthur Weasley/Weasley twins- ENTP.
No doubt about it- they love experimenting, Arthur is fascinated with Muggle's- something that not the average wizard would be interested in. Arthur is clever, intelligent, and yet very loyal and supportive of his family, which may argue with ENTP- but his overall character is ENTP...The twins- obviously ENTPs- very playfull, always pulling pranks, are extremely ingeniuos, clever, and are always inventing things- hense the name "Inventor" for ENTP.
Ginny: INTJ
Could be open to anything, though I'm leaning towards INTJ or maybe ISTJ. She seems pretty straightforward, and quiet.
Snape: INTP
I know there is a lot of fuss about him being an INTJ, but you must look into him. He lives a terrible life, was made fun of all throughout school, and struggled with what side he belonged to, though we know he was loyal to Dumbledore. He is an overall mystery throughout most of the storyline, he's very intelligent, witty, dark, and clever (INT). I'm saying P for I can see the internal struggles he was constantly facing, and how not straightforward he is. If he was a J, he'd be a little easier to understand and type and straightforward.
Voldemort: INTJ
NO WAY IS HE AN ENTJ, as is clearly states numerous times throughout the 6th and 7th for his want of solitude, and how he preferred to do things on his own. He had is own agenda- his own plan and stuck with it. He was curious, extremely intelligent, and sort of self absorbed, though he lived a tragic life. He had a small exclusive group of followers and was never open to any of their ideas, and never ever talked about himself or his life. INTJ fits Voldemort like..like..something that fits another thing very well!
Lupin: INFP
Lupin was the quiet, sensative, secretive on of the group when he was in school with james, sirius, and peter. His story was a secret, and only his friends knew for a long time of his second life. He treated Harry as an individual (Fi), and overall gave off a very seclusive, quiet, mellow vibe- INFP.
Sirius/James- ESTP
Sirius and James were pranksters, and goofed off quite a bit, as we so often were told throughout the stories. Though they both may also be ESFPs, the two of the were warriors at heart, and stood up against the evil in the world.
Neville: ISFP
Neville is a lot like Harry, surprisingly, yet they have both lived two very different lifes. He is quiet, self conscious, has a low self esteem, and is a very curious kid. He is frank, kind, and you can't not like him. He sticks up for his values- as seen in the 5th book where he tries to avenge his parents when he meets Bellatrix. He has lived a sad life, almost as sad as Harry's, but we have to infer that as the story is of Harry's perspective, in a way.
Recap:
Harry: ISFP
Ron: ESFP
Hermione: ISFJ -> INFJ
Dumbledore: INFJ
Hagrid: ISFJ
Snape: INTP
Draco: ESTP/ESTJ
Arthur/Weasley Twins: ENTP
Ginny- INTJ/ISTJ
Voldemort: INTJ
Lupin: INFP
Sirius/James- ESTP (maybe ESFP).
Neville: ISFP
House types-
Gryffindor- xSFP - the value warriors
Hufflepuff- xSTJ - the equality supervisors
Ravenclaw- xNxJ- The intellectual wisemen
Slytherin- xxTJ - the exclusive purebloods
Further...
Molly Weasley- ESFJ
Luna Lovegood- INFP
Trelawney- INTP
McGonnigal- ENTJ
Dobby- ESFP
Kreacher- ISTP
Dudley- ISTJ
Vernon- ESTJ
Petunia- ISTJ
Cedirc Diggory- ENFP