Finally, for those eager to run from Afghanistan, let me just stay that P.L. 107-40 (or try this--the PDF link seems loopy) did not declare war on Osama bin Laden:
That the President is authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons.
Did we defeat all the nations, organizations, or persons that did or might in the future carry our or assist in future attacks? No.
Those idiots unfurling the "mission accomplished" banner after we killed bin Laden have such a limited grasp of strategery that it defies common sense to listen to them about anything more significant than what they'd prefer to have for dinner.
Continue the mission.
UPDATE: Oh, and if we want to kill the ideas of Osama bin Laden and ultimately defeat that ideology of hate, checking out of the war is exactly the wrong message to send. Jihadis will see Osama's death as one of a martyr who in the end defeated America simply by dying for the cause and exposing the hollowness of American will to win.