Astronomy 161: Neptune: General features and some pictures.
Encarta Encyclopedia: Neptune: Information on the planet Neptune.
Exploring the Planets: Neptune: Information and photographs on the moons, atmosphere, and rings of planet Neptune
John Couch Adams and Neptune: The History of its discovery.
Mathematical Discovery of Neptune: Another interesting history on how planets can be discovered mathematically.
Neptune: Pictures, statistics, and detailed information on planet Neptune.
Neptune114: Its atmosphere, rings, moons, appearance, and links to related sites.
NSSDC Photo Gallery: Neptune: Select images of the planet, with brief captions.
Royal Greenwich Observatory: Neptune: Basic overview.
Views of the Solar System: Neptune: Views, animations, general information and data of the planet.
Welcome to the Planets: Neptune: Planetary profile and vital statistics.
Windows to the Universe: Neptune: Overview of several aspects of the planet. Versions available for beginner, intermediate and advanced level users.