It's Michael Griffin...
...for NASA Administrator, according to the White House announcement this afternoon.

Mr. Griffin currently heads the Space Department at the Johns Hopkins University Applied Physics Laboratory. If confirmed by the Senate, he likely will push boldly to implement President Bush's plans for exploration of the Solar System. He will also have the opportunity to reconsider the options for the future of the Hubble Space Telescope. It's not clear where Mr. Griffin will come down on this question.