The National Map, a part of the USGS National Geospatial Data Program, is a good resource for both digital maps and gis data for the United States. From the National Map site: "The National Map is a collaborative effort among the USGS and other Federal, State, and local partners to improve and deliver topographic information for the Nation. It has many uses ranging from recreation to scientific analysis to emergency response. The National Map is easily accessible for display on the Web, as products and services, and as downloadable data. The geographic information available from The National Map includes orthoimagery (aerial photographs), elevation, geographic names, hydrography, boundaries, transportation, structures, and land cover."
The National Map is currently accessible through four different frequently updated viewers:
The National Map Viewer is the face of The National Map and allows the user to interactively view The National Map data as a map, customize the view, and print maps.
The National Map Seamless Server enables a user to view and download many geospatial data layers, such as the National Elevation Dataset, the National Land Cover Dataset, high resolution orthoimagery, and other seamless data for the Nation.
The National Map Best Practices viewer contains our most up-to-date vector data for transportation, structures, and governmental units data themes.
The National Map National Hydrography Dataset (NHD) viewer contains our most up-to-date, full featured hydrography data.
Continuing with the Sanborn map theme, the San Francisco Public Library (SFPL) has recently created an e-card option for California residents. Anyone who lives in California can register for an e-card that will allow users to access the SFPL's online databases, streaming audio and video, ebooks and audiobooks, and business databases for job seekers, among other resources.
Regarding maps, the SFPL e-card grants access to both the Sanborn map subscription and EBSCOHost's Magazines' image collection. The Sanborn maps for California number about 660,000 and are dated from between 1867-1970. The EBSCOHost Magazine image collection contains over 202,000 images, maps, and flags.
The SFPL's e-card expires after 4 years and is non-renewable. For long term access to the SFPL collection, e-card users can upgrade to a full access card for a fee. The SFPL provides a FAQ with further questions and answers.
The University of Nevada, Reno (UNR), as part of its Nevada in Maps collection, has made Sanborn maps of 29 Nevada towns available online for free. The dates of the maps range from 1879 through 1923. From the site: "Nevada's early western settlement history was one of tenuous existence. Settlements, hardly towns much less cities, came and went usually as mining sites were exploited and declined. Few maps exist to document the existence and changes to these towns . . . This project is an effort to present online a full-color set of Nevada SanbornŽ and other Nevada town maps. There is no full set in any format available at any location in the state."
The site also features a very useful set of links that include information about Sanborn maps, information about the UNR map project, an inventory of various formats of Nevada town maps online, and a site that details the coordination between Sanborn maps and historic photographs of specific buildings in Nevada.
The National Library of Scotland has made over 8,000 maps, originally published between 1560 and 1935, available online. The digital maps are high resolution, zoomable scans that users can zoom and pan over with or without the use of a browser plug-in.
The map subjects include: all of Scotland, county maps, town plans/views, coasts of Scotland, military maps, Bathymetrical Survey of the Fresh-Water Lochs of Scotland, series maps, and estate maps. Users can also search the holdings and browse by mapmaker. The About page gives examples of many of the different types of maps available. Many of the maps are also available as digital overlays for Google Maps and Google Earth.