USFWS National Digital LibraryAnother fantastic site linking to other U.S. government sites containing hundreds of thousands free and public domain images linking to image categories such as Air Force, forests, animals, Army, birds, coast guard, crops, fish, fire, fruits, geology, Indians, lab research, mammals, money, mountains, NASA, Navy, parks, plants, Presidents, space, storms, veggies, volcano's, war, wildlife, and much more.