Health On the Net Foundation
Guides lay persons and non-medical users and medical practitioners to useful and reliable online medical and health information. Provides leadership in setting ethical standards for Web site developers.
http://www.hon.ch/

WebMD
Resource for consumers, physicians, nurses, and educators. Includes news, chat forums, health quizzes and consumer product updates.
http://www.webmd.com/

BBC Health
Features current news plus archives, guides by subject, "Ask a Doctor", searchable conditions database, message board, and e-mail newsletter subscription.
http://www.bbc.co.uk/health/