NOAA Space Environment Center -- The official U.S. government bureau for real-time monitoring of solar and geophysical events, research in solar-terrestrial physics, and forecasting solar and geophysical disturbances.
Solar and Heliospheric Observatory -- Realtime and archival images of the Sun from SOHO. (European Mirror Site)
Daily Sunspot Summaries -- from the NOAA Space Environment Center.
Current Solar Images --a gallery of up-to-date solar pictures from the National Solar Data Analysis Center at the Goddard Space Flight Center.
Recent Solar Events -- a nice summary of current solar conditions from lmsal.com.
SOHO Farside Images of the Sun from SWAN and MDI.
The Latest SOHO Coronagraph Images -- from the Naval Research Lab
The Sun from Earth -- daily images of our star from the Big Bear Solar Observatory
List of Potentially Hazardous Asteroids -- from the Harvard Minor Planet Center.
Observable Comets -- from the Harvard Minor Planet Center.
What is the Interplanetary Magnetic Field? -- A lucid answer from the University of Michigan. See also the Anatomy of Earth's Magnetosphere.
Real-time Solar Wind Data -- from NASA's ACE spacecraft.
More Real-time Solar Wind Data -- from the Solar and Heliospheric Observatory Proton Monitor.
Aurora Forecast --from the University of Alaska's Geophysical Institute
Daily Solar Flare and Sunspot Data -- from the NOAA Space Environment Center.
Lists of Coronal Mass Ejections -- from 1998 to 2001
What is an Iridium flare?
Vandenberg AFB missile launch schedule.
What is an Astronomical Unit, or AU?
Mirages: Mirages in Finland; An Introduction to Mirages;
NOAA Solar Flare and Sunspot Data: 1999; 2000; 2001; Jan-Mar., 2002; Apr-Jun., 2002; Jul-Sep., 2002; Oct-Dec., 2002;
Recent International Astronomical Union Circulars