There are several free online sources for maps.
The CIA World Factbook provides current maps of countries across the globe. Page Size Base maps are in the public domain. Accordingly, they may be copied freely without permission of the Central Intelligence Agency (CIA).
NATO on the Map is an interactive map of NATO forces and operations in Europe and The Middle East. The website has multiple layers of information, which you can access through the side navigation bar. You can also find photos, videos and news articles on NATO activities, Allies and partners.
The Perry-Castañeda Library Map Collection from the University of Texas at Austin provides maps of current and historical interest.
The David Rumsey Map Collection provides historical maps of the world. For historical maps of the United States, you can view The Library of Congress Map Collection.