Ancient World Mapping Center (AWMC): "promotes cartography, historical geography and geographic information science as essential disciplines within the field of ancient studies through innovative and collaborative research, teaching, and community outreach activities."
ArcGIS Online: "ArcGIS Online provides a series of 2D map services and 3D globe services that can be used to support your GIS work. These ready-to-use services can be accessed with any ArcGIS application—for example, with ArcGIS Explorer, ArcMap, ArcGlobe, or ArcReader..." from the webpage.
Broer Map Library: "a large collection of government, commercial and other produced maps and atlases from the past three centuries. The library endeavers to provide its collection of maps and atlases online in order to allow libraries and researchers who would not otherwise have access to such a large collection, have them available."
David Rumsey Map Collection: "the David Rumsey Historical Map Collection has over 14,800 maps online. The collection focuses on rare 18th and 19th century North and South America maps and other cartographic materials. Historic maps of the World, Europe, Asia and Africa are also represented. Collection categories include antique atlas, globe, school geography, maritime chart, state, county, city, pocket, wall, childrens and manuscript maps. The collection can be used to study history, genealogy and family history."
d-maps.com : contains more than 5900 high definition outline maps, each one proposed in 6 graphic formats (GIF, PDF, CDR, SVG, AI, WMF)
The Lionel Pincus and Princess Firyal Map Division (New York Public Library) The collection is primarily focussed on New York City and the State of New York. Includes atlases of NYC, Sanborn Map Company insurance maps of the 5 boroughs, topographic maps and aerial maps
Images of Early Maps on the Web: "the only comprehensive listing of its kind, comprising over 1,200 annotated links - updated at least every two months".
Map Collections from American Memory, Geography and Map Division of the Library of Congress. Images from the Americana and Cartographic Treasures of the Library of Congress "created from maps and atlases and, in general, ... restricted to items...not covered by copyright protection.
NatGeo Mapmaker Interactive Customize one-page maps and download, email, print, or share!
Office of Coast Survey's Historical Map & Chart Collection "covers the land and waters of the United States of America, including territories and possessions (past and present). The images are free to download, and may be used for commercial or educational purposes.. . . The collection also covers many areas that most people may not realize were once a part of early Coast Survey history. As the first federal scientific agency, the U.S. Coast and Geodetic Survey (as the agency was known from 1878 to 1970) produced land sketches, Civil War battle maps, and aeronautical charting from the 1930s to the 1950s."
Outline Maps: outline maps which may be printed and copied for personal or classroom use.
Perry-Castaneda Library Map Collection: online map collection from the University of Texas at Austin.
Physical Atlas of Europe: "Geography relief of Europe maps, clickable mountains and rivers maps, countries, towns and European Union maps, Europe cities pictures and landscapes images"
Strange Maps - A Blog: a blog website displaying and describing unique and unusual maps!
USGS Map Databases: several online map indexes which can be used to locate, view and create maps. Includes the National Map and the National Atlas of the United States.
Vemap: Free Vector Maps: The Vector Map (VMAP), also called Vector Smart Map, is a vector-based collection of geographic information system (GIS) data about Earth at various levels of detail.