Tom Ridge resigns, according to CNN.
UPDATE: This story seems to have dropped off the radar. Perhaps it was premature. Here is one of the only things I could find when Googling now: Talk Radio News Service:
Tom Ridge Resignation
In response to the question of whether Secretary of Homeland Security Tom Ridge was resigning, McClellan answered that there was no announcement to be made but that the White House would keep the media informed at the appropriate time about any announcement.