If you are in the Boston area, I would highly recommend Tufts University Emergency Veterinary Clinic, as Matese listed above. Here is a link to their webpage:
24-Hour Pet Emergencies, Walpole, MA | New England Veterinary Critical Care . The level of care from vet school hospitals is usually unsurpassed in my experience. Also, if you call them and describe the symptoms, they can help you decide whether to bring your dog in.