http://sunsite.berkeley.edu/libweb/ 

 Links to over 2,500 Libraries in over 70 countries:

http://www.loc.gov/  

USA Library of Congress

http://www.sil.si.edu/  

Smithsonian Institute Libraries

http://www.gutenberg.net/ 

Project Gutenberg

http://www.earthinstitute.columbia.edu/library/ 

Columbia Earth Institute