For the Consumer
USP DI volume II Advice for the Patient - see Micromedex above.
Medline Plus Drugs & Supplements - Prescription and over-the-counter medication information from AHFS Consumer Medication Information.
Safemedications.com - Searchable database based on ASHP's AHFS Consumer Medication Information.
MayoClinic.com - Drugs and Supplements
PDR Guide to Over-the-counter drugs - based on FDA-approved drug information found in PDR.
British National Formulary (Free registration required)