Flipper. According to Raw Story, sources have identified the senior cooperating witness in the CIA leak investigation. No word yet on who is cooperating, but one possibility is our old dear pal, Ari Fleischer. Ari isn't a longtime Shrub loyalist, he only joined the cabal after Libby Dole dropped out of the primaries in 2000. He does, however, have ties to the Bush crime family dating back to when he worked as Poppy's deputy communications director.
I don't think it's Colin Powell. Lots of people think this will be his great redemption, but I doubt it. And whoever they flipped must have been involved, and I'd believe that Colin wasn't intimately tied up in this. And I don't think that Rove would have flipped to save his own ass because he probably still believes that he's too smart for Fitzgerald. And Andy Card is probably too busy getting hamburgers.
Anyway. If Ari has been flipped, that would certainly explain this bit from the Wikipedia entry on Asshat.
Fleischer has been suggested as being a second leaker in the Valerie Plame affair, in which one or more members of the White House staff leaked Plame's identity to the press. Plame was a covert agent with non-official (NOC) cover status in the CIA and the publication of her name resulted in her cover being blown.1Ari's lawyers haven't returned any calls for a long time. Ari also has a young child, so he probably isn't looking for an extended stay in the pen.
On July 18, 2005, Bloomberg reported that in his sworn testimony before the grand jury investigating the leak, Fleischer denied having seen a memo circulating on Air Force One on July 7, 2003 which named Plame in connection to Wilson's mission and which identified her as a CIA covert agent. However, a former Bush Administration official also on the plane testified to having seen Fleischer perusing the document. 
Columnist Robert Novak, who published Plame's name on July 14, 2003, made a call to Fleischer on July 7, 2003 before Fleischer's trip to Africa with the President. It is unclear whether Fleischer returned Novak's call.
No matter what, after two years of following this case, it'll be interesting to see what comes of it all.