Harvard University - Map Collection - Library history, general information, an overview of map collections, and an online exhibit of Civil War map images.
Library of Congress - Geography and Map Division - History and background of the geography and map division, and reference services and guides. Includes a large, searchable collection of online North American maps in the public domain, dating from 1544 to present.
Maps, Plans and Charts - Provides access to item-level descriptions from the "old map card catalogue" of the National Archives of Canada. About 4,000 items have been digitized and may be consulted online.
University of Colorado at Boulder - Map Library - General information and tour, recent acquisitions, collection descriptions, and annotated links to map resources and digital spatial data.