MDConsult and FirstConsult BMJ Clinical Evidence Dynamed Trip Plus Database EMedicine from WebMD Epocrates drug database Clinical Trials Database Clinical Trials.gov Clinical Trials Database National Cancer Institute Clinical Practice Guidelines National Guideline Clearinghouse Cochrane Library of Systematic Reviews U.S. Preventive Services Taskforce Guidelines from U.S. Department of Health and Human Services Merck Medicus - Textbooks, best practices, journals, CME. Requires free registration Emedicine.com Clinical Significance / Number Needed to Treat Calculator