The African-American Mosaic is a Library of Congress resource guide for the study of black history & culture.

The Avalon Project provides primary sources relevant to the fields of law, history, economics, politics, diplomacy, and government. The resources are organized by era and may be perusable by category: ancient history, medieval history, and the 15th century to the present.

Chronicling America allows you to search and view American historic newspapers, published 1836-1922, as well as more newspapers published in the U.S., 1690-present.

The Cornell University Library Making of America Collection is a digital library of primary sources in American social history from the antebellum period through reconstruction.  The collection is particularly strong in the subject areas of education, psychology, American History, sociology, religion, and science and technology.

Digital History focuses on American History from the earliest days through the 20th century.  The site features a wealth of classroom-ready resources including links to primary sources, lesson plans, quizzes, and more.

The Digital Public Library of America brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world.

DocsTeach is available from the National Archives. Find and create interactive learning activities with primary source documents that promote historical thinking skills.

Duke University’s Digital Collections contains several primary sources related to American history, the arts, advertising and consumer culture, and more.

The Gilder Lehman Institute of American History awesome site that tells you whether a link is a Primary Source or not.  Features several links to online exhibitions and primary source documents. The collection ranges from 1493 through the twentieth century and is widely considered one of the nation’s great archives in the Revolutionary, early national, antebellum and Civil War periods.

Library of Congress’ The American Folklife Center provides online access to selected portions of their collections. They create their own online presentations on various topics and the American Memory project provides additional online access to selected collections. Online content may include audio samples of music and stories, digital images of rare letters and photographs, and video clips. 

Library of Congress Prints and Photographs Online Catalog is unique in their scope and richness, the picture collections number more than 15 million images. These include photographs, historical prints, posters, cartoons, documentary drawings, fine prints, and architectural and engineering designs. While international in scope, the collections are particularly strong in materials documenting the history of the United States and the lives, interests, and achievements of the American people.

The Labyrinth from Georgetown University provides several resources about medieval studies including primary and secondary sources.

Life Magazine Photo Archive  lets you look through images organized by decade (1860s through 1970s) or significant people, places, events or sports topics.

The National Archives holds the records of the United States Federal government. On-line access to art works, census data, U.S. legal manuscripts, the Federal Register and more.  Searchable for many primary sources.

Primary Documents in American History this website contains documents from the years 1775 to 1872. Updates will be made on a regular basis.

Science and Medicine Research Guide - This guide links to several primary and secondary sources for topics related to science and medicine. Of interest is links to the Newton Papers, the Alexander Graham Bell Family Papers, and collections of rare books on plague and epidemiology.

The Smithsonian’s Library and Archival Exhibitions on theWeb contains a vast searchable collection of digitized collections and archives from around the world.