National Atlas of the United States data. Various map layers downloadable in an ESRI shapefile format that can be used in geographic information, desktop mapping, and computer-aided design systems.
Coverage is from the federal level on down to the local level in some cases.
And Mostly Free U.S. Geospatial and Attribute Data CIA World Map Database - The map data itself consists of coastlines, rivers, lakes, international political boundaries, US state boundaries, and Canadian province boundaries. Most of the data is free to download, but you do have to pay if you want a cdrom. The level of mapping is designed to be used for broad planning and management uses covering state, regional, and multi-state areas. This level of mapping is designed for use by landowners, townships, and county natural resource planning and management.