US aircrafts of World War II

12 O'Clock High!: Very detailed information about the Luftwaffe, including information about the paint schemes, markings and cannons, as well as some information about the US VIII Air Force. Also includes forums about both the Luftwaffe and Allied air forces
American Aces of WWII: Biographical information and scores of US aces of World War II, as well as information about the most famous US aircrafts. Also includes a section on German aces and World War I aces
Dave's Warbirds: Very extensive information about the aircrafts and air forces of the US, and information about the US carrier-based air warfare in the Pacific
European Center of Military History: Very extensive photo archive, with a lot of exellent photographs, primarily of Allied soldiers and materiel