Lots of primary sources from the 15th to the 18th centuries.
US Naval Heritage and History Command
The NHHC manages the official history program of the United States Navy, The website contains photographs, official records, and multiple artifact links providing a very detailed repository for US Naval documents.
Library of Congress Digital Collections
Images, documents (original images with transcriptions), etc.
US National Archives
US Online archives including maps, letters, documents, photographs, film, audio recordings, and lesson plans for teachers. Content always being added.
Digital Public Library of America
Harvard based digital archive containing 33,658,432 images, texts, videos, and sounds from across the United States.
Old Bailey Online (UK)
A fully searchable edition of 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.
Fordham University Internet History Sourcebook
A collection of public domain and copy-permitted historical texts presented cleanly for educational use. Grouped by category, some are abreviated and others in full.
Chinese Kuomintang (KMT) Archives Microfilm Project at the Hoover Institution.
Over 100,000 documents from the Kuomintang government in China. Trace the evolution from warlord band, Allied recognized "official" government of China, through the defeat by the CCP/USSR coalition in 1949 to exile on Taiwan.
This online treasure trove holds extensive collections of primary source materials and publications in the field of military law via the Library of Congress Federal Research Division (FRD) Web site. Source documents on legal issues from the Indian Wars, Civil War, WWII, Korea, and Vietnam are highlighted in special collections.