| Marie Curie | Marie Curie Cancer Care |
| Medline | US National Library of Medicine |
| Medical Ethics | The Pro Life Organisation |
| Medical World Search | Great Medical Search Engine |
| Medexplorer | The Great Medical & Health Search Engine for All (US) |
| MedNets | International Research Site |
| Masta On-line, Health Abroad | Minding Your Health Abroad |
| ME Association | ME Information Site |
| MS Society,The | UK Multiple Sclerosis Site |
| MIND | UK Mental Health Charity |
| Mental Health Net | IT for Health Care |
| Mental Health Foundation | UK Mental Health Information Site |
| Mayo | The Mayo Clinic USA |
| Meningitis | Comprehensive UK Help Site |