Per this HuffPo article:

Perhaps the most remarkable moment of the interview, however, came when Cheney was asked if President Bush himself had signed off on the interrogation program. His response left the impression that Bush was brought into the loop only as a legal or political formality.

"I certainly have every reason to believe that he knew a great deal about the program," he said. "He basically authorized it. I mean, this was a presidential level decision. And the decision went to the president. He signed off on it."

There is also this from Condi Rice:

Questioner: "Is water boarding torture?"

Rice: "The President instructed us that nothing we would do would be outside of our obligations, legal obligations, under the Convention Against Torture. So that’s, and by the way I didn’t authorize anything, I conveyed the authorization of the administration to the agency that they had policy authorization subject to the Justice Department’s clearance, that’s what I did."

Questioner: "Is water boarding torture, in your opinion."

Rice: "And I just said the United States was told, we were told, nothing that violates are obligation under the Convention Against Torture, and so by definition if it was authorized by the President it did not violate our obligations under the convention against torture."

There is also the memo that Jason Leopold wrote about in which FBI personnel mention a Bush authorization: http://emptywheel.firedoglake.com/2009/04/30/a-bush-eo-on-torture/

There is also this LA Times story, where White House spokesman Tony Fratto “indicated that Bush might consider reauthorizing waterboarding or other harsh techniques in extreme cases, such as when there is “belief that an attack might be imminent.”