They Drew Fire - Companion site to the PBS documentary on combat artists of World War II features an art gallery, artist biographies, and resources.
Trench Art of the Great War - Information on art made during WWI, including prisoner of war art, decorated equipment, and shell art.
U.S. Army Official War Artists - Profiles of the eight World War I artists, plus a look at how their work was carried out and how it was received back home.
World War II Navy Art: A Vision of History - Exhibit of works by Navy artists who served in combat areas and recorded their impressions of the action. Includes captions in the artists' own words.