Health Illustrated Encyclopedia on Merck Source
Online dictionary free to the public, by Merck & Co.
Medline Plus: Drugs, Supplements and Herbal Information
National Library of Medicine consumer health resource offering an alphabetical index of drugs by generic or brand name from MedMaster as well as an index of herbs and supplements from Natural Standard.
Medline Plus: Medical Encyclopedia
Online free Medical Dictionary from the National Library of Medicine, National Institutes of Health, and Department of Health & Human Services.