In an interview with the Today Show, JK Rowling revealed who the character is that received a reprieve in Deathly Hallows.
(SPOILER)Arthur Weasley
Additionally, Jo announced that she "probably will" create a Harry Potter encyclopedia! From NBC's website:
The encyclopedia would include back stories of characters she has already written but had to cut for the sake of narrative arc (“I've said before that Dean Thomas had a much more interesting history than ever appeared in the books”), as well as details about the characters who survive “Deathly Hallows,” characters who continue to live on in Rowling’s mind in a clearly defined magical world.