What would cause a grinding noise when you let off the breaks slowly?

on newer volvos, and many other cars, the grinding you might hear is simply the sound the brake pads make when they rub against the brake rotor. if you let off the brake slowly, then its purely the slight friction between the two causing the sound. i too have an s60 and have heard this before. dont worry about it. the s60 is a heavy car and the brakes are under a lot of pressure