Government

• The National Institutes of Health
  The primary U.S. medical and disease research agency

Health Guides

• Medline Plus
  A guide from the National Institutes of Health
• WebMD
• Women's Health Guide (MedicineNet)
• Kid's Health
  For Parents, Kids and Teens

Major Hospitals

• The Mayo Clinic

Pharmacies

• Walgreens

Medical Journals

• Entrez
  Includes PubMed and Genome and Protein Databases
• American Journal of Clinical Nutrition
• The Obesity Research Journal
• The New England Journal of Medicine
• The Lancet
• JAMA - The Journal of the American Medical Association

Exercise

Nutrition

• Wellsphere - Health knowledge made personal