There are many references sources that area available online for free. Below are links to many of these sources with a brief description about the site.

Library of Congress Collections- This database contains free images and primary source documents from a variety of topics.

Artcyclopedia- This database contains information about artists, artworks, art museums, and movements.

Bartleby- This database contains full text versions of classic literature. Literary criticisms are also included.

Directory of Open Access Journals- This database contains free peer reviewed articles and journals that apply to any subject area.

EDGAR- This database provides information on companies and is maintained by the government.

FedStats- This database contains statistics about various government agencies and departments.

HathiTrust- This database provides free access to a wide range of materials.

Homeland Security Digital Library- This site contains government documents about various issues pertaining to Homeland Security.

Hoover's- This site contains information on an extensive list of companies.

Human Rights Library- This site contains information on United Nations documents.

Internet Archive- This database provides free access to materials that are culturally significant to the United States.

Perseus Digital Library- This site provides information on early English literature and culture.

State Library of Pennsylvania Digital Collections- This site provides links to various documents housed by the State Library of Pennsylvania.

THOMAS- This government database houses various bills, reports, and other government resources.

World Factbook- This database provides information on various countries. This site provides information on culture, statistics, and other resources.