Hermione answered like the good little student she was. "Well one was a family heirloom, Harry said it had the symbol for Slytherin house on it. Then there was the diary, that one seems a bit weak of an option if you ask me, who would embed their soul in paper? Harry also mentioned Voldemort's snake, Nagini.. So I suppose it could be anything. Harry said Dumbledore thinks there might be an item from every founder at Hogwarts, although where anyone would find them I don't know." 