Medical 

• Encyclopedia of Life Sciences

Published by the Nature Publishing Group, accessible through STAT!Ref as an eBook

• 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.