The best location for topographic maps is the USGS store (
http://store.usgs.gov). Direct to the store is at:
http://store.usgs.gov/scripts/wgate/ZWW20/%21?%7Elanguage=en&%7Etheme=GP&OSTORE=USGSGP&%7EOKCODE=START
Select the Map Locater and Downloader option. This allows you to locate the area and lets you know what maps are available. The downloaded maps are GeoPDFs -- which can be used as regular PDFs or with the free plugin you can use some measuring tools.
If you have a printer or application that can tile a print job, this could actually be useful.
Of course, you could always just buy the thing for $6.00 . Probably cheaper in the long run and much less trouble.
Someone on this forum posted a nice web site that adds topographic maps, Aerial photos, and NEXRAD data to google maps.
http://mapper.acme.com/-Tommy