This may have been answered before in the thread, but I didn't see it on a quick read-through.
I'm using the NewPing library (which is awesome) and the Arduino Motor Shield. Unfortunately the shield uses pins 3 and 11 to do the motor PWM, which conflicts with Timer2 used in NewPing.
Is there a way to change what timer NewPing uses? Or, is it just simpler to un-stack the shield and the Arduino and manually wire the PWM into different pins?