National Library of Medicine (NLM) Resources - lets users search resources previously accessed through the NLM Gateway. Contains a comprehensive list of databases, resources and API's.
The Free Dictionary: Medical Dictionary - The Free Dictionary's main source is is The American Heritage® Stedman's Medical Dictionary, Second Edition, which provides authoritative descriptions of medical conditions, medications, anatomical terms, noted medical personalities and much more.
Science.gov: A gateway to government science information and research results. Provides a search of over 36 scientific databases and 200 million pages of science information with just one query, and is a gateway to 1,850+ scientific Websites.