NASA
Nasa: Kepler and His Laws
This site from NASA provides biographical details about the lives of Tycho Brahe and Johannes Kepler. Discusses Kepler's successes at developing laws of planeatry motion. States the three laws and discusses each one individually....
Georgia State University
Georgia State University: Hyper Physics: Kepler's Laws
An outstanding page describing Kepler's three laws of planetary motion.
NASA
Nasa: Kepler's Second Law
This site from NASA states Kepler's second law of planetary motion and depicts its meaning with an informative diagram. Relates the law to conservation of energy principles and discusses the eccentricity of a satellite's (or a planet's)...