USGS web map services

The USGS makes a number of their map products available as a WMS Web Map service. These layers are available to use as a backdrop in GIS software, such as ArcGIS or the free, open-source, QGIS.

See http://viewer.nationalmap.gov/example/services.html for a list of the services. Use the Link found under the WMS column in your GIS software of choice.