CIA World Factbook - Current demographic information for every country in the world, includes political, economic, social and geographic information.
D-Maps.com - More than 187,000 maps available in various formats.
Encyclopedia Britannica - Includes information, maps and other geography-related images.
GapMinder - Site offers data on more than 500 indicators, plus stunning videos in which much of the data is brought to life visually.
Google Maps - Create your own using GIS - Using the Google Maps platform, create your own map with layers, annotations, pins, etc. Each map can host up to ten different layers. The possibilities are infinite.
Google Public Data - Customizable data from a HUGE plethora of sources. Visualize selected data in a variety of modes.
National Geographic - The name says it all. Check out their MapMaker Interactive for personalized, digital maps.
NationMaster - A source of varied country-specific data; multiple countries can be compared graphically.
Perry Casteñeda Library Map Collection (University of Texas) - An indispensable site for locating thousands of historical and contemporary maps.
United Nations Development Programme (UNDP) - Human Development Index - This UN agency site offers country profiles, national reports, and comparative rankings on multiple development indicators.
World Atlas - A basic website that contains sound geographical information; good for background research.
World Bank - A reliable source for a crazy amount of data that can be organized by country, topic or scores of specific indicators.
Worldmapper - A fascinating collection of world maps, where territories are re-sized on each map according to the subject of interest.