The American Museum of Natural History is developing Digital Universe, a downloadable 3D tool that enables you to explore the universe.

The free map viewer Celestia “lets you explore our universe in three dimensions.”

NASA also has a free map viewer World Wind which is open-source. There is an extensive documentation site at World Wind Central.

Google Earth Pro includes layers for Earth, Sky, Moon, and Mars, plus the Flight Simulator.

Harvard University’s Center for Geographic Analysis has developed the WorldMap tool, which allows you to “build your own mapping portal and publish it to the world.”

Need to geocode a large number of addresses?  Try TAMU Geoservices for geocoding, reverse geocoding, and address parsing and standardization.

ColorBrewer offers color advice for cartography and has been carefully designed to be a diagnostic tool for evaluating the robustness of individual color schemes.