Barewalls
The barewalls online catalog of posters and prints according to subject-matter. this subject catalog includes these subject categories: agriculture, animals, anthropomorphism, architecture, botany, celebrities, children's art, commercial art, communications, doors, fashion, figures, film, food and beverage, golf, landscape, london, military, monet's waterlilies, music, nautical, new york, paris, philadelphia, portraits, religion, seascape, smithsonian collection, smoking, space, sports, sports panoramas, still life, transportation, urban, verbs and vintage advertising.
http://www.barewalls.com/indexes/military.html
Northwestern
Information on world war 2 posters. the government publications department at northwestern
university library has a comprehensive collection of over 300 posters
issued by u.s. federal agencies from the onset of war through 1945.
http://www.library.northwestern.edu/govpub/collections/wwii-posters/
Worldwar1
An history of the great war of 1914 to 1918 presented in internet format. contains various articles and features from authors around the world. please be aware this is a hi-bandwidth site.
http://www.worldwar1.com/posters.htm