The National Center for Health Statistics - Information on births, deaths, ageing, disease classification and other health statistics.

Ask the Medical Expert - Answers to medical related queries searchable from archives of the weekly column.

AskDrWalker - Resources and links to medical information. Includes medical databases, medical search engines, diseases and conditions and useful links for health professionals and patients.

Best Evidence Topics - Access to evidence-based medicine topics. Includes a searchable database.

Building Better Health - Medical and healthcare information on disease and health improvement topics. Includes medical news, clinical research and newsletters.

CDC Health Topics A to Z - A listing of disease and health topics from the Center for Disease Control and Prevention in the United States.

Centre for Medical Web Research - A virtual centre for researching medical questions on the internet.

DiagnosisHeart.com - Information on heart disease with surgical data and related resources.

DocMD.com - Provides links to free medical and medically-related sites.

Doctor NDTV - Information on a variety of health issues from medical experts. Includes FAQ.

Doctor's Desktop - Tables and charts for practicing medical professionals. It also provides an ECG course by e-mail.

The Doctors Page - Links to patient education materials, medical reference sites and medical humor.

eMedicine - Consumer Treatment Guidelines - Textbook on the treatment of common medical problems.

Globalrph - Provides drug information, intravenous drug dilution standards and online clinical dosing calculators for health care professionals.

Harrison's Online - Regularly updated online version of the medical textbook. Subscription required with free 4-week trial.

Health Information Library - Alphabetical listing of health information topics by the Carle Clinic and Hospital.

Healthsites UK - A portal to medical and health information for patients and doctors. Access medical and NHS healthcare sites plus news, advice and complementary therapy resources.

The Homeless Handbook - An online manual designed to assist support workers of homeless and similarly disadvantaged people who find themselves in medically challenging situations.

Library of the National Medical Society - Links to various journals, online diagnosis, medical textbooks and atlases. Subscription required.

Longevity Healthy Aging Research Group - Information from this Canadian organisation on getting older and staying healthy.

MD Consult - Includes reference books, journal search, practice guidelines, patient education and drug information. Subscription required, free trial period.

MedCalc - A collection of online clinical calculators. Includes ABG, GFR, Fluids and BMI calculations and interpretations.

MedConnect - Information services with a clinical and practical focus for physicians and other health care professionals.

Medical Knowledge Base - Offers discussion forums on topics like cancer, AIDS, arthritis, hepatitis, healthy nutrition and motivation.

Medics Travel - Lists hospitals, charities, NGOs and recruitment agencies around the world to help doctors, nurses and medical students plan work and electives overseas.

Mediresource - Information on diseases and conditions, support groups and drug information. Primarily patient-oriented.

MedPix - Database of medical images including radiology, pathology, and dermatology. Case of the Week with CME for physicians and CNE for nurses.

The Merck Manual - Online version of The Merck Manual of Diagnosis and Therapy.

MerckMedicus - Links to health resources for patients, professionals and an online medical library.

My Body - Interactive symptom checker, includes details of some possible causes.

NCEMI: Common Simple Emergencies - An online manual with detailed instructions and illustrations on how to treat various everyday medical emergencies.

OHSU Health - Information for patients and clinicians on aspects of healthcare. Includes an index of health topics.

PolyMedicine.com - Clinicians review electronic medical information resources available in any of the following media: browsable WWW sites, downloadable datasets and software or CD-ROMS.

Predictonline - A testing and awareness site to provide the public and healthcare provider with medical information on various medical conditions.

PreventDisease.com - A patient-oriented portal for up-to-date health information on fitness, lifestyle, nutrition and health tools.

RJ's Medical Directory - A collection of medical links and information categorized by specific topics.

South African Health Information - Reviewed, evidence-based health information based on the South African health system.

Talk Medical - Offers information on diseases, disorders, medications, parenting, and pregnancy. Also includes a searchable medical dictionary.

Virtual Naval Hospital - A digital library designed to help primary care providers and to help patients associated with naval medical issues. A service of the U.S. Navy Bureau of Medicine and Surgery.

Virtual Pediatric Hospital - A digital health sciences library at the University of Iowa for health care providers and patients.

Well-Connected - Offering over 100 in-depth reports on physical and mental diseases and wellness issues. Written by medical writers and reviewed by a board at Harvard Medical School. Some information available free but most requires paid access.