“Now the pitch, and it's lined foul into the seats, down the third base line, 1 ball, 1 strike, and I'll tell you what's going on. The crowd is chanting "U-S-A!" and the reason for that is that there are reports circulating, I'm not sure if they yet been confirmed by the White House, that Osama bin Laden is dead. How that's happened, we don't know, but this crowd now knows it.”

This misquotation is frequently attributed to a White House press conference, March 13, 2002 http://georgewbush-whitehouse.archives.gov/news/releases/2002/03/20020313-8.html
Correct quote should read: "And, again, I don't know where he [Osama Bin Laden] is. I — I'll repeat what I said. I truly am not that concerned about him."
The relevant parts of the White House transcript reads:
: THE PRESIDENT: Deep in my heart I know the man is on the run, if he's alive at all. Who knows if he's hiding in some cave or not; we haven't heard from him in a long time. And the idea of focusing on one person is — really indicates to me people don't understand the scope of the mission. Terror is bigger than one person. And he's just — he's a person who's now been marginalized. His network, his host government has been destroyed. He's the ultimate parasite who found weakness, exploited it, and met his match. He is — as I mentioned in my speech, I do mention the fact that this is a fellow who is willing to commit youngsters to their death and he, himself, tries to hide — if, in fact, he's hiding at all. So I don't know where he is. You know, I just don't spend that much time on him, Kelly, to be honest with you. I'm more worried about making sure that our soldiers are well-supplied; that the strategy is clear; that the coalition is strong; that when we find enemy bunched up like we did in Shahikot Mountains, that the military has all the support it needs to go in and do the job, which they did.
: Q: But don't you believe that the threat that bin Laden posed won't truly be eliminated until he is found either dead or alive?
: THE PRESIDENT: Well, as I say, we haven't heard much from him. And I wouldn't necessarily say he's at the center of any command structure. And, again, I don't know where he is. I — I'll repeat what I said. I truly am not that concerned about him. I know he is on the run. I was concerned about him, when he had taken over a country. I was concerned about the fact that he was basically running Afghanistan and calling the shots for the Taliban.
Attributed, Misquotations