MEDLINEplus Drug Information
http://www.nlm.nih.gov/medlineplus/druginformation.html

Drug, supplement and herbal information from the AHFS Consumer Medication Information (prescription and over-the-counter information)and on herbs and supplements from the Natural Standard

CenterWatch Drug Directories
http://www.centerwatch.com/drug-information/index.htm

Offers a range of free, easy-to-search resources on drugs in various stages of development and approval .

DrugDigest
http://www.drugdigest.org/wps/portal/ddigest

A consumer health and drug information website from ExpressScripts, Inc. featuring a drug, vitamin and herbal library in addition to a drug interactions database

FDA's Center for Drug Information and Research
http://www.fda.gov/cder/

Features consumer drug information, over-the-counter drug information and information on clinical trials

RxList - The Internet Drug Index
http://www.rxlist.com/script/main/hp.asp

Owned and operated by WebMD and part of the WebMD network.

U.S. Pharmacopeia

http://www.usp.org/

Lists standards for prescription and over-the-counter medicines and other health care products manufactured or sold in the United States