ORIGINS
Site about the origin of the universe. Created by NASA.
http://origins.jpl.nasa.gov/

DESTINATION: EARTH
Official Website for NASA's Earth Science Enterprise, an organization that studies the Earth's environment.
http://www.earth.nasa.gov/

WELCOME TO THE PLANETS
Facts about and physical characteristics of the planets of the solar system. Site created by the California Institute of Technology sponsored by NASA.
http://pds.jpl.nasa.gov/planets/

SOLAR SYSTEM EXPLORATION
Homepage created by NASA.
http://sse.jpl.nasa.gov/index.cfm

SPACEZONE
Homepage has interesting diagrams. Site created by Explorezone.com.
http://www.livescience.com/space/