That he choreographed the title dance scene in Jailhouse Rock (it was based on his stage moves, but JR had a choreographer).
That he had bone cancer.
That he stole Hound Dog from its writer, Big Mama Thornton (this one was extremely popular for a few years).
And this seems to be a good thread to mention this one: that he had an affair with June Carter before she married Johnny Cash. Carter Cash's son mentions this in his book on his mother (which is fascinating reading for anyone who thinks there was a shred of truth in the movie Walk the Line, by the way). And I've seen an interview with June Carter in which she claimed that Elvis had a massive crush on her.
This one was new to me - I thought Anita Carter was the one that interested Elvis. Does anyone know if there's any truth in it?