MedicationAdvisor http://www.medicationadvisor.com/
Provides computer-generated analyses of the safety of a drug profile, including interactions, side effects, dosing, and hazards. (Advanced, highly detailed reports are available as a subscription.)
MedicationSense http://www.medicationsense.com/
Contains informative articles written by a physician who is a recognized expert in the field of medication side effects. Articles are designed to provide an objective analysis of topical issues related to drug therapy.
MedLibrary.org http://medlibrary.org/
Provides free access to a medication database covering roughly 500 drugs, plus a regularly-updated selection of the latest medical news headlines.
MJ Powers and Co. http://alertpubs.com/
Offers a number of drug alert newsletters dealing with the safety and efficacy of drugs and therapies in that particular discipline. [Requires Java]