Embase is a large biomedical database with a strong focus on the literature on drugs and devices. It also contains a large number of international studies.
Access Medicine provides access to major medical textbooks including Harrison's Principles of Internal Medicine. It also provides practice guidelines, diagnostic tests, and a variety of self-assessment tools.
The Cochrane Library is a collection of databases that includes the Cochrane Database of Systematic Reviews and the Cochrane Central Register of Controlled Trials.
Micromedex provides drug information, including drug interactions, drug comparisons, and drug ID. Micromedex also provides free access to several drug information apps.