History: Military (Univ of Washington) offers lists of numerous digital collections
The Papers of the War Department (1784-1800)
Civil War (US)
Spanish American War
World War I
World War I: A Resource Guide lists online sources at the Library of Congress and beyond.
CENDARI Transnational Archive Directory is a large database of archival descriptions from over 1,000 institutions, European and worldwide. It is focused on medieval and World War I resources.
The First World War: Two sections: Personal Experiences, Propaganda and Recruitment. Largely British. Some material from the Hoover Institution Library.
Mission Centenaire 14-18 includes maps, photos, oral histories, post cards and other documents about the First World War from French archives.
Propaganda Poster Digital Collection (Washington State University) includes 520 World War I and World War II posters.
Western European Theater Political Pamphlet Collection 1894-1918 (Princeton University Library). Topics include the economy, the press, the military, arms, territorial disputes, and others. The collection also includes speeches, sermons, bulletins, calendars, and songbooks. Material in English, German, French, Italian, Russian, and other languages.
Women, war and society, 1914-1918 documents women’s contribution to the war. Includes charity and international relief reports, pamphlets, photographs, press cuttings, magazines, posters, correspondence, minutes, records, diaries, memoranda, statistics, circulars, regulations and invitations. Reproduction of originals from the Imperial War Museum, London.
World War One (British Library) offers over 500 historical sources (together with interpretative essays .
WWI & WWII Posters: UBC Library Digital Collections - Fifty nine posters, broadsides, and ephemera from World War I and II, published in Canada, Belgium, England, France, Germany, and the United States
Spanish Civil War
World War II
World War II Internet sites: a vast selection of World War II digital collections online from Bowling Green State University
Conditions & politics in occupied Western Europe, 1940-1945 consists of documents from the British National Archives on the German-occupied countries.
World War II, occupation, and the Civil War in Greece, 1940-1949: records of the U.S. State Department Classified Files
National socialism, Holocaust, resistance and exile 1933-1945, and Daily reports of the Gestapo Headquarters Vienna 1938-1945 contains about 40,000 primary sources on the National Socialist state and the NSDAP, Nazi ideology and propaganda, National Socialist justice and legislation, on resistance and persecution, and annihilation and expulsion in the "Third Reich".'
World War II, occupation, and the Civil War in Greece, 1940-1949: records of the U.S. State Department Classified Files partment papers in FO 371. Section I: Japanese Imperialism and the War in the Pacific, 1931-1945 -- Section II: Occupation of Japan, 1946-1952 -- Section III: Japan and Great Power Status, 1919-1930.
World War II oral history project focuses on the American home front experience.
La France pendant la guerre 1939-1945 : résistance et journaux de Vichy = Voices from wartime France 1939-1945 : clandestine resistance and Vichy (Archives unbound.) constitutes the sum of the French press that reached Britain during the Occupation of 1940-44. Reproduction of the originals from the British Library.