Centers for Disease Control and Prevention (CDC) - Diseases and Conditions A-Z Index
FamilyDoctor.org - (American Academy of Family Physicians)
Healthline - (Healthline Media)
MayoClinic.com (Mayo Clinic) - Patient Care and Health Information
Merck Manuals Consumer Version (Merck) - Android version available here; Apple version available here.
National Institutes of Health (NIH) - Health Information
Everyday Health - (Everyday Health Inc.)
MedNar (Deep Web Technologies) - start at Advanced Search to find health-related sites on the Web.