Wizards and muggles alike, take note! Author J.K. Rowling has conjured up a title for her sixth Harry Potter novel: Harry Potter and the Half Blood Prince. She's also spilled some tantalizing plot clues on her official Web site. "The Half Blood Prince is neither Harry nor Voldemort," Rowling wrote, "and that's all I'm saying on that subject until the book's published." What a tease.