Yes, there are several laws that provide broad protections to different groups of people when they provide assistance to injured or incapacitated persons.  Massachusetts General Laws Chapter 111C, Section 21 protects EMS personnel:
 
Section 21. No EMS personnel certified, accredited or otherwise approved under this chapter, and no additional personnel certified or authorized under section 9, who in the performance of their duties and in good faith render emergency first aid, cardiopulmonary resuscitation, transportation, or other EMS, to an injured person or to a person incapacitated by illness shall be personally liable as a result of rendering such aid or services or, in the case of an emergency medical technician or additional personnel, as a result of transporting such person to a hospital or other health care facility, nor shall they be liable to a hospital for its expenses if, under emergency conditions, they cause the admission of such person to said hospital.
 
Chapter 112, Section 12V protects the general public:
 
Section 12V. Any person, whose usual and regular duties do not include the provision of emergency medical care, and who, in good faith, attempts to render emergency care including, but not limited to, cardiopulmonary resuscitation or defibrillation, and does so without compensation, shall not be liable for acts or omissions, other than gross negligence or willful or wanton misconduct, resulting from the attempt to render such emergency care.
 
And, finally, Chapter 112, Section 12B protects doctors, nurses, and other medical professionals:
 
Section 12B. No physician duly registered under the provisions of section two, two A, nine, nine A or nine B, no physician assistant duly registered under the provisions of section nine I or his employing or supervising physician, and no nurse duly registered or licensed under the provisions of section seventy-four, seventy-four A or seventy-six, or resident in another state, in the District of Columbia or in a province of Canada, and duly registered therein, who, in good faith, as a volunteer and without fee, renders emergency care or treatment, other than in the ordinary course of his practice, shall be liable in a suit for damages as a result of his acts or omissions, nor shall he be liable to a hospital for its expenses if, under such emergency conditions, he orders a person hospitalized or causes his admission.