Do you use your rear brake?

From the man himself:

The fastest that you can stop any bike of normal wheelbase is to apply the front brake so hard that the rear wheel is just about to lift off the ground. In this situation, the rear brake cannot contribute to stopping power, since it has no traction.

http://www.sheldonbrown.com/brakturn.html

This man is right. However it also can result in a face plant.

He is accurate in that you cannot stop faster by any other method aside from a full on collision with a unmoveable object.

To avoid face plant, use a back brake too.