Global Land Environments Since the Last Interglacial. Quaternary paleomaps from Dr. Jonathan Adams of the University of Adelaide, with detailed descriptions of climatic change over time.
National Map - The Nation's Topographic Map for the 21st Century (USGS). Online, interactive mapping for the United States, provided by a group of partners (Federal, State and Local).
Paleomap Project. Offers detailed maps showing the positions of the continents during different geologic eras.
This Dynamic Planet. This map shows the Earth's physiographic features, the current movements of its major tectonic plates, & the locations of its volcanoes, earthquakes, and impact craters.
USGS Online Map Lists. Provides information exclusively on USGS published topographic maps.
Geographic Names Information System. This immensely useful site allows you to search for information on named geographic features, providing data on latitude and longitude, limited population data, and references to USGS maps.