The house finders:
Salazar Slytherin
Salazar is one of the four finders of Hogwarts. A power thirsty friend to the others, he is responsible for the building of chamber of secrets. He falls out with the other 3 when he wanted students to be picked more carefully, leaving out muggles. He is also related to Voldemort. His house is famous for being the bad people. Everyone in his house are pure bloods. We can see his appearance on the chocolate frog cards and the statue in the chamber of secrets and a portrait of him in the School. Salazar is one of the earliest recorded people with parstle mouth. Salazar's locket was one of the horcruxes (some of the front covers of the last book have this locket as the image) but this was destroyed by Ron Weasly. His house logo is a snake and element is water.
Helga Hufflepuff
Helga was one of the four founders, and was unique as the other fours chose children with special talents, where as Helga accepted any (but her house kids are described as loyal and hard working). She is described as sweet and good. We have evidence of what she looks like as her portrait is at Hogwarts. Helga's famous for her food related charms, and some of her recipes are used at the modern school feasts today. She also came up with the idea of house elves working in kitchens where they can't be abused. Voldemort used her goblet as one of his horcruxes (the cup was from a descendant) which was destroyed by Hermione. In May 2007, on Rowling's website, Helga was wizard of the month. Her house logo is a badger and element is earth.
Godric Gryffindor
Godric was one of the four founders of Hogwarts and was good friends with Salazar until they fell out. He is described as the best duellist of his time. He chose students who are brave and determined. Godric was one of Hogwarts first headmasters. When he fell out with Salazar, Salazar left the school. We don't know how or when he died, but his legacy is the sorting hat. His portrait hangs at the School. He also left his goblin made sword which Harry used to kill the Basilisk. The sword was also used to destroy many of the horcruxes, including Salazar's locket and Nangini (whom Neville killed). The main characters are mostly in Gryffindor. It is possible that Harry is a descendant of his. The name Godric means he who rules with god or he who rules well. The logo of his house is the lion and element is fire.
Rowena Ravenclaw
Rowena Ravenclaw is one of the four founders of Hogwarts. She's famous for her wisdom and creativity and was described ad beautiful. The sorting hat says she is fair and form glen (so perhaps she's from Scotland). Rowena's daughter Helena stole her diamen and ran away to Albania. Rowena sent someone after her and she was murdered there (Helena is Ravenclaw's house ghost) by the bloody baron, in love with Helena ans guilty, he took his own life. Rowena created the idea of the moving staircases. She picks smart students for her house. She created the phrase 'wit beyond measure is a man's greatest pleasure'. Having smart people in her house, an eagle knocker asks students a riddle to which they must answer to get in. Her house logo is an eagle and element is air.