Another useful site is http://viewer.nationalmap.gov/viewer/ which is a Google Maps like interface that allows downloading map data, topos, and other data files.
The Libre Map Project has a copy of the data (they were really hard to find for a while) and allows searching for feature names and downloading TIFFs of USGS quadrangles, TFW files, and TIGER files.
Another useful site is http://viewer.nationalmap.gov/viewer/ which is a Google Maps like interface that allows downloading map data, topos, and other data files.
There's also some web APIs available for retrieving and querying the data at http://basemap.nationalmap.gov/arcgis/rest/services
The Libre Map Project has a copy of the data (they were really hard to find for a while) and allows searching for feature names and downloading TIFFs of USGS quadrangles, TFW files, and TIGER files.
http://libremap.org/data/