A:
Ask Dr. SOHO - Answers questions about the Sun [National Aeronautics and Space Administration (NASA)]

Ask Mr Sunspot - Questions are answered about the Sun, Moon, planets, stars, and other astronomical topics [National Science Foundation (NSF), National Optical Astronomy Observatory (NOAO), National Solar Observatory]

Astrogeology Research Program - Primary homepage for the Astrogeology Research Program with links to solar system, space missions, technology, data & information, research programs for geology, remote sensing, and ice & polar, hot topics, photo gallery, and Astro Kids [Department of the Interior, U.S. Geological Survey (USGS), Astrogeology Research Program]

G:
Gamma Ray Large Area Telescope (GLAST) - Information on the high-energy gamma-ray observatory designed for making observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 100 GeV [National Aeronautics and Space Administration (NASA)]

Goddard Space Flight Center - Sciences and Exploration Directorate - Enables space-based exploration of the Earth, the Solar System, and the Universe through scientific leadership and innovation. [National Aeronautics and Space Administration (NASA), Goddard Space Flight Center (GSFC)]

H:
High Altitude Observatory (HAO) - Focuses on the numerical simulation of convection, radiation transport, and large-scale dynamics in both the solar and terrestrial atmospheres, plus measurement of the Sun's output of magnetized plasma and radiation [National Science Foundation (NSF), National Center for Atmospheric Research (NCAR)]

N:
NTRS (NASA Technical Reports Server) - Search for reports, journal articles, and conference proceedings [National Aeronautics and Space Administration (NASA)]

O:
Optical Long Baseline Stellar Interferometry News - A forum for scientists, engineers, and students where you will find links to projects devoted to stellar interferometry, news items, and resources for further research [National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL)]

S:
Solar Physics. - Access to solar research. [National Aeronautics and Space Administration (NASA), Marshall Space Flight Center (MSFC)]

Solar System - Provides information on the planets, the Sun, asteroids and comets, solar system missions, and images and videos [National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL)]

Solar System Simulator - Creates a color image of a planet or its satellite [National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL)]

Solar and Heliospheric Observatory - Information and daily images and movies of the Sun from the SOHO mission. [National Aeronautics and Space Administration (NASA)]