Many familiar sites use satellite images as basemaps, for example Google Maps or Map Quest.
Most satellite imagery requires that you download and learn to use more specialized software, either a commercial product or an open source product such as Multispec.
Many sites that have recent photos, also contain older photos. Sources include Federal government sites and various repositories. Some imagery is available for free; other imagery must be purchased.
Libraries or other institutions may maintain collections of local historical photos. University of Michigan Library listed below maintains a lengthy list of links to other areas, arranged by states.
Sources of U.S. imagery include:
State-level GIS data repositories, state cartographer offices, or other government agencies may provide access to recent air photos and imagery and/or maintain archives of historical aerial photos. Some examples include
