Digital Atlas of the United States 2000: http://www.cdvision.com/
All of the data layers compiled by the USGS as part of their National Atlas of the USA Project, plus elevation and geology. (Note, the 2000 web site will open within the Digital Atlas Navigation, otherwise you will get caught in their frames page!)

Digital Chart of the World: http://www.maproom.psu.edu/dcw/
Download and preview boundaries of individual countries and data layers in ArcInfo export from Penn State University.

Digital Earth Initiative: http://digitalearth.gsfc.nasa.gov/
A virtual representation of Earth that enables exploration and interaction with natural and cultural information about the planet.

National Atlas of the United States: http://www.nationalatlas.gov/
An interactive atlas designed to promote greater geographic awareness through easy to use, map-like views of the natural, cultural and social landscapes of earth.

National Geographic Atlas of the World: http://plasma.nationalgeographic.com/mapmachine/plates.html
Detailed geographic maps of the world.

Nature Mapping Program in Washington: http://www.fish.washington.edu/naturemapping/
Home page of the Nature Mapping Program in the state of Washington. This is a good place to learn about native terrestrial and aquatic species in that state, as well as to see the educational outreach capabilities of the Internet in practice.

Raven Maps and Images: http://www.ravenmaps.com/
This site is the on-line gallery of Raven Maps and Images. They combine beautifully colored cartographic art, with highly detailed topographic maps. Maps are available for purchase via the site.