Diagnosis and Treatment

Medical imaging

Radiology Info
Information on radiology/medical imaging (X-ray, MRI, CT, ultrasound, and others) from the American College of Radiology and the Radiological Society of North America

Surgery

Canadian Anesthesiologists' Society 
Information on anesthesia from the Canadian Anesthesiologists' Society

Labs

Lab Tests Online 
Provides information on many clinical lab tests

Emergencies

Mayo Clinic First Aid Guide 
First-Aid Guide produced by the Mayo Clinic

Medications/Drugs

Drugs, Supplements, and Herbal Information by MedlinePlus
From the U.S. National Library of Medicine and the U.S. National Institutes of Health (NIH)

Health Canada 
Drug product database contains product specific information on drugs approved for use in Canada

Health Canada - Med Effect
Health product safety database

Health product safety database

U.S. Food and Drug Administration 
Medication guides with FDA-approved information

Herbs and Supplements

Health Canada 
Licensed Natural Health Products Database is managed by Health Canada

Medline Plus: Drugs, Supplements and Herbal Medications 
Information from the U.S. National Library of Medicine and the National Institute of Health