Any document, image, or artifact created at the time of the topic being researched is first-hand evidence and thus a primary source.
RhinoCat is the Library's automated catalog of books, ebooks, DVDs, and other library materials. Many books and reference sources, print and electronic, contain primary sources.
British History Online (digital library containing some of the core printed primary and secondary sources for the medieval and modern history of the British Isles)
Children and Youth in History (resources on the experience of childhood and adolescence, including hundreds of primary sources; from George Mason University)
EuroDocs (Primary sources for European history, many with English transcriptions; from Brigham Young University library)
German History in Documents and Images (introduction to key developments in Germany's social, political, and cultural history by period with primary sources, images, and maps)
Hanover Historical Texts Collection (from Hanover College)
Internet History Sourcebooks Project (Vast collection of primary sources from Prof. Paul Halsall, Fordham University)
London Lives 1690-1800: crime, poverty and social policy in the metropolis (Information and a wide range of primary sources, digitized and searchable, about the lives of real eighteenth-century Londoners; "Lives" and "Historical Background" are especially useful pages)
Old Bailey Online: London's central criminal court, 1674-1913 (the largest body of texts detailing the lives of non-elite people ever published, containing 197,745 criminal trials held at London's central criminal court)
Primary Source Nexus: World History and Culture Resources (collaboration between the Library of Congress and archives, libraries, and museums in Europe)