Here's my initial short list, certain to be expanded as we learn more (unless, of course, they cover it up):
George W. Bush, President of the United States
Michael Chertoff, Secretary of the Department of Homeland Security
Michael Brown, Under Secretary of Homeland Security (FEMA Director)
Kathleen Babineaux Blanco, Governor of Louisiana
C. Ray Nagin, Mayor of New Orleans
I suggest they time their resignations to ensure no further harm is done by their leaving.