Hogwarts

Harry Potter - Gryffindor
Ron Weasley - Gryffindor
Hermione Granger is a Gryffindor
Sirius Black
The Weasley family: Arthur and Molly (Ron's parents), Bill, Charlie, Percy, Fred and George (brothers), Ginny (sister) - Gryffindor
Albus Dumbledore
Minerva McGonagall
Severus Snape (Snape)
Rubeus Hagrid
Filius Flitwick
Pomona Stem (Sprout)
Dolores Umbridge
Remus Lupin
Hortense Slughorn (Slughorn)
Voldemort
Draco Malfoy - Slytherin
Lucius Malfoy
Bellatrix Lestrange
Peter Pettigrew
Bartemius Crouch Jr.
Neville Longbottom - Gryffindor
Luna Lovegood - Ravenclaw
Cedric Diggory - Hufflepuff
Zhou Chang - Ravenclaw
Ginny Weasley - Gryffindor
Fred and George Weasley - Gryffindor
Dobby the House Elf
Kreacher is a house elf.
Alastor Moody (Mad-Eye)
Kingsley Shacklebolt
Nymphadora Tonks
Oliver Wood - Gryffindor
Angelina Johnson - Gryffindor
Fawkes is Dumbledore's phoenix.
Hogwarts Ghosts: Nearly Headless Nick (Gryffindor), Bloody Baron (Slytherin), Gray Lady (Ravenclaw), Fat Friar (Hufflepuff)
Vincent Crabbe - Slytherin
Gregory Goyle - Slytherin
Pansy Parkinson - Slytherin
Theodore Nott - Slytherin
Blaise Zabini - Slytherin
Lee Jordan - Gryffindor
Dean Thomas - Gryffindor
Seamus Finnigan - Gryffindor
Parvati Patil - Gryffindor
Lavender Brown - Gryffindor
Cormac McLaggen - Gryffindor
Angelina Johnson - Gryffindor
Katie Bell - Gryffindor
Rowena Ravenclaw - Ravenclaw
The Gray Lady - Ravenclaw Ghost
Padma Patil - Ravenclaw
Roger Davis - Ravenclaw
Michael Corner - Ravenclaw
Terry Booth - Gryffindor
Helga Hufflepuff was the founder of the house. She valued hard work, loyalty, and honesty; she took under her wing all who wished to study.
Ernie MacMillan - Hufflepuff
Hannah Abbott - Hufflepuff
Justin Finch-Fletchley - Hufflepuff
Susan Bones - Hufflepuff
Zachariah Smith - Hufflepuff
Megan Jones - Hufflepuff
Wayne Hopkins - Hufflepuff
Tom Riddle - Slytherin
Gellert Grindelwald