From Football Outsiders "The Week in Quotes":
“It’s the most overrated thing in sports.”
– Peyton Manning, on whether one team can gain an advantage by signing players who have recently been released from an upcoming opponent
“‘I’m telling you, Peyton’s going to change it up. He knows I’m here, he’s going to give you a dummy audible early. I’m telling you, he’s not stupid. So, just play your keys.’”
– Manning, describing information quarterback Kelly Holcomb (who had recently been cut by the Colts) funneled to the Browns in 2002 before the two teams played each other
“Second half, we get a good drive going and it’s fourth-and-3. So we run our bread-and-butter play, a little five-yard under route. Well, I signal the play and Holcomb — it’s the same signal — so he says, ‘Ah, now I’m going to help them.’ So he says, ‘They’re running the five-yard under play! Five-yard under play!’”
– Manning, still building to the payoff
“And so you can see it on the film — they’re going, ‘Watch the slants, watch the slants.’ So they load up, all inside technique, and they go into a man defense. Well, I see this and I see the defenders all change up — that’s the thing about the no-huddle, I can see this — and I kept the receivers doing the same thing and I checked to a zone running play and it’s only six guys who gotta know — the linemen and the back [James Mungro]. And he goes 29 yards untouched for a touchdown.”
– Manning, not quite there yet
“And so their guys go to Holcomb, all pissed off, ‘So, they’re running a slant, huh? Thanks a freaking lot, Holcomb.’”
– Manning, dropping the hammer

I've always suspected that the whole 'give away the playbook' bit was crap. . .especially in this day and age of free agency (so everyone is going between teams) and customized game plans week in, week out.