Here is a long list of highly-reputable sites. However, Defibrillators.com does NOT endorse any of these sites, nor claim affiliation with them, nor vouch for their content, as it may change day-to-day.

Scientific Conferences
Scientific Sessions
International Stroke Conference

U.S. Government Sites
Centers for Disease Control
   
Food and Drug Administration (FDA)   
healthfinder
National Center for Health Statistics   
National Heart, Lung, and Blood Institute (NHLBI)   
National Institute of Neurological Disorders and Stroke   
National Institutes of Health   
National Library of Medicine 
U.S. Department of Health and Human Services   
U.S. Department of Agriculture

Associations and Societies
American Alliance for Health, Physical Education,
Recreation and Dance (AAHPERD)
   
American College of Cardiology   
American College of Physicians   
American Dietetic Association   
American Medical Association   
American Pregnancy Association
American Red Cross   
American Society of Echocardiography   
American Society of Hypertension   
American Society of Nuclear Cardiology   
Association of American Medical Colleges
Cardiovascular Research Foundation (CRF)
Heart Failure Society of America, Inc.
The Henry J. Kaiser Family Foundation
National Aphasia Association   
AEDHelp.com
American Heart Association

National Center for Early Defibrillation
The Future of Defibrillators
Delicious Decisions
Pictures of Defibrillators
The American Diabetes Association
Advanced external Defibrillators
Just Move!
Rental of Defibrillator Rentals
Cheap Defibrillators
Fitness Clubs and AED's

The National Registry of CardioPulmonary Resuscitation   
North American Society for Cardiac Imaging   
Pulmonary Hypertension Association   
Society of Cardiovascular & Radiology & Interventional Radiology
Society for Cardiovascular Pathology
Society of Invasive Cardiovascular Professionals   
Society of Thoracic Surgeons   
Vascular Surgery Societies

Universities and Research Centers
American Association of Medical Colleges (list of Medical Schools)   
Johns Hopkins Bayview – Division of Cardiology   
Stanford Stroke Center   
Yale University School of Medicine

International Organizations
British Heart Foundation   
Canadian Cardiovascular Society
European Institute of Healthcare
European Society of Cardiology
German Heart Foundation
Global Cardiology Network   
Heart Foundation of New Zealand   
Heart Foundation of South Africa   
Heart and Stroke Foundation of Canada   
InterAmerican Heart Foundation   
International Federation of Red Cross and Red Crescent Societies   
International Society for Heart and Lung Transplantation   
International Society of Adult Congenital Cardiac Disease,
The Canadian Adult Congenital Heart Network and the
Toronto Congenital Cardiac Centre for Adults
   
Mediterranean Stroke Society   
Northern Ireland Chest Heart & Stroke Association   
World Health Organization – Cardiovascular Diseases   
World Heart Federation