At Terminal 4 near the West end baggage claim level, doggies can stretch their little legs. The "Bone Yard" is a great pet-and-their-people rest area. It includes watering areas, a gravel area for potty breaks, and "mutt mitts" for cleaning up.
In Terminal 3, the "Paw Pad" is a fenced area with water spigots and bowls, paw shaped decorations, and a fun red fire hydrant.