From the USGS website:

• USGS Topographic Maps
  Most USGS topographic maps use brown contours to show the shape and elevation of the terrain.
• USGS Business Partners for Maps
  This web site is designed to help customers find and contact USGS Business Partners that retail USGS maps. Although USGS hosts this site as a service to the Business Partner network, specific information on each retailer is maintained by that retailer.
• Map Information
  Learn about, locate, view, download, or order topographic, geologic, and other special purpose maps and charts in a variety of printed and digital formats.
• How to Order Products from the USGS
  This page provides ordering information for the wide range of products available for sale from the USGS.
• Map Prices
  Current price information for maps available from USGS can be found here.
• Topographic Map Symbols
  A topographic map shows more than contours. The map includes symbols that represent such features as streets, buildings, streams, and vegetation.

Downloads:

• Map Order Form (PDF)
  Use this form to order USGS maps, books, and other published products by mail or fax.
• Topographic Map Symbols (PDF)
  A topographic map shows more than contours. The map includes symbols that represent such features as streets, buildings, streams, and vegetation.
  

Other links:

• Greenberg & Lieberman
  Greenberg & Lieberman is an Intellectual Property Law Firm, which is registered to practice before the U.S. Patent and Trademark Office (USPTO). It is the firm that wrote and filed the patent for the TopoCover™.
• TopoZone
  You can easily browse through a complete list of every USGS topo map by name, or look through lists of place names sorted by type or by county. Just click on a state name below to start browsing.