When in doubt if the information in the website is reliable, use this Library guide checklist.
The U.S. National Library of Medicine also has a page on Evaluating Internet Health Information.
International
Canadian Institute for Health Information (CIHI)
CADTH - Canadian Agency for Drugs and Technologies in Health
Health Canada, Radiation - Technical Reports and Publications and Safety Codes
Medical Apps for Radiology - Regularly updated list of medical apps (for iPhone/iPod Touch--fee)