National Library of Medicine
The National Library of Medicine (NLM), on the campus of NIH in Bethesda, Maryland, is the world's largest medical library.
Oclc.org
OCLC Online Computer Library Center is a nonprofit, membership, computer library service and research organization whose computer network and services link thousands of libraries worldwide.
http://www.oclc.org/
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The Internet Archive
Features the Wayback Machine, which makes it possible to surf pages stored in the Internet Archive's web archive.