Here are some basic sites to find relevant information. Government and educational sites are the most reliable sites. Check out the Evaluating Resources page for how to find reliable websites.

American History

Library of Congress American Memory provides free and open access through the Internet to written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music that document the American experience.

American Rhetoric 5000+ full text, audio, and video (streaming) versions of public speeches, sermons, legal proceedings, lectures, debates, interviews, and other recorded media events.

In the first person is an index to letters, diaries, oral histories, and other personal narratives with more than 3,350 collections of personal narratives in English from around the world. Keyword search more than 650,000 pages of full-text by more than 15,000 individuals.

Presidents: Selected speeches of all the U.S. presidents, with an emphasis on inaugural and State of the Union speeches, plus writings and biographies, maintained by George M. Welling, University of Groningen, The Netherlands.

American Memory Archival material relating to American culture and history from the Library of Congress; includes papers of Presidents Washington, Jefferson and Lincoln, WPA life histories, images, sheet music, etc.

World History

Internet Modern History Sourcebook Covers European history and American history, as well as in modern Western Civilization and World Cultures.

Internet Medieval Sourcebook Full-text primary and secondary sources, including Ancient, Medieval and Byzantine hagiographical sources.

Internet Ancient History Sourcebook A guide to full-text ancient history sources on the web.

History Net is brought to you by the Weider History Group, the world's largest publisher of history magazines. HistoryNet.com contains daily features, photo galleries and over 1,200 articles.

The Victorian Web Deals with many aspects of the Victorian Period. From Brown University.

Mapping History: The Darkwing Atlas Project Maps of Europe, Asia and North America.

Cultural Maps Historical geography of America from the University of Virginia.

Panoramic Maps, 1847-1929 Collection from the American Memory Project of the Library of Congress.

Periodical Historical Atlas of Europe Available in English and French, this atlas consists of maps "depicting with accuracy the state of this continent every day of each centennial year from AD1 to AD 1700".
 

American Historical Association was founded in 1884 and incorporated by Congress in 1889 to serve the broad field of history. It encompasses every historical period and geographical area and serves professional historians in all areas of employment. 

The Organization of American Historians is the largest learned society devoted to the study of American history.