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.
Atmospheric Optics -- the first place to look for information about sundogs, pillars, rainbows and related phenomena.
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 -- from the National Solar Data Analysis Center
Recent Solar Events -- a summary of current solar conditions from lmsal.com.
What is the Magnetosphere?
The Lion Roars -- visit this site to find out what the magnetosphere sounds like.
List of Potentially Hazardous Asteroids -- from the Harvard Minor Planet Center.
Observable Comets -- from the Harvard Minor Planet Center.
Real-time Solar Wind Data -- from NASA's ACE spacecraft.
How powerful are solar wind gusts? Not very! Read this story from Science@NASA.
More Real-time Solar Wind Data -- from the Solar and Heliospheric Observatory Proton Monitor.
Lists of Coronal Mass Ejections -- from 1996 to 2006
Mirages: Mirages in Finland; An Introduction to Mirages;
NOAA Solar Flare and Sunspot Data: 1994, 1995, 1996, 1997, 1998, 1999; 2000; 2001; 2002; 2003; 2004; 2005; Jan-Mar 2006; Apr-Jun 2006; Jul-Sep 2006; Oct-Dec 2006.