Photostock
Wikipedia says: "Stock photography consists of existing photographs that can be licensed for specific uses. Book publishers, specialty publishers, magazines, advertising agencies, filmmakers, web designers, graphic artists, interior decor firms, corporate creative groups, and other entities utilize stock photography to fulfill the needs of their creative assignments. By using stock photography instead of hiring a photographer to perform on-location shooting, customers can save valuable time and stay on budget. With a wealth of images, stock photography databases that may be searched online save photo researchers valuable time when they are looking for just the right image. With today's digital delivery methods, images may be purchased online and delivered via email or downloaded right away."
fotosearch: directory of Royalty Free and Rights managed Stock Photography, Illustrations, and Clipart
stock.xchng: good quality free and low cost stock photography with clear rights declarations
creative commons, images: Creative Commons is a nonprofit organization that offers flexible copyright licenses for creative works.