Helios - A Space Weather Center: Has some good information on Space Weather, as well as some links to other pages.
http://www.astro.lu.se/~henrik/heliosspwsc.html
 

International Solar-Terrestrial Physics (ISTP): NASA’s International Solar-Terrestrial Physics page, exploring the Sun-Earth Connection.
http://www-istp.gsfc.nasa.gov/
 

The NASA Space Weather Bureau: Simple page with news, forecasts and trivia.
http://spaceweather.com
 

National Space Weather Program: contains the NSWP Strategic Plan [1995].
http://www.geo.nsf.gov/atm/nswp/nswp.htm
 

Space Environment Center (NOAA): Has Press Releases, Events, and other information concerning Space Weather.
http://www.sec.noaa.gov
 

Today's Space Weather (SEC/NOAA): SEC issues solar forecasts and monitors conditions in geospace.
http://www.sec.noaa.gov/today.html
 

Space Weather at Rice University: Has lots of information, movies and images on Space Weather, Aurorae, and Earth’s Magnetosphere.
http://rigel.rice.edu/~freeman/dmb/spwea.html
 

Space Weather Resources at the NSSDC: Provides resource materials for conducting space weather related research and educational activities.
http://nssdc.gsfc.nasa.gov/space/spdf/space_weather/Space_Weather_at_SSDOO.html 
 

University of Oulu (Finland) Space Physics Textbook: In-Depth information about Space Weather and Space Physics.
http://www.oulu.fi/~spaceweb/textbook/
 

Windows to the Universe Space Weather page: current space weather conditions for the solar wind and magnetosphere.
http://windows.engin.umich.edu/spaceweather/
 

SAMPEX: Information and data from SAMPEX, the first of the SMEX (SMall EXplorer) spacecraft. Among other things, SAMPEX studies high energy particles in Earth's radiation belts and upper atmosphere.
http://lepsam.gsfc.nasa.gov/www/sampex.html
 

Solar:

SOHO: The Solar and Heliospheric Observatory: Has great solar images from SOHO and information on the SOHO mission.
http://lepsam.gsfc.nasa.gov/www/sampex.html
 

Stanford Solar Center: Lots of educational activities from the team of SOHO's Solar Oscillations Investigation.
http://solar-center.stanford.edu/
 

Sunspots and the Solar Cycle: A page sponsored by NASA’s Marshall Space Sciences Lab, with good, well organized information on the solar cycle, sunspots and the effects of solar activity on the earth.
http://www.sunspotcycle.com/
 

YOHKOH SXT Home page: Images, Movies and news from the YOHKOH Soft
X-Ray Telescope (SXT).
http://www.lmsal.com/SXT/
 

The National Solar Observatory: Descriptions of the Sacramento Peak and Kitt Peak Solar Observatories, as well as a digital library of images which includes current solar images.
http://www.nso.noao.edu/
 

The Global Oscillation Network Group (GONG): GONG is a community-based project to conduct a detailed study of solar internal structure and dynamics using helioseismology. Their page contains information about the project as well as a gallery of images.
http://www.gong.noao.edu/
 

Aurora:

The Aurora Page: Information, links and images on the Northern Lights, Aurora Borealis.
http://www.geo.mtu.edu/weather/aurora/
 

Aurorae, Paintings in the Sky: What are auroras? What makes them happen? What do they look like? Where can you see
them? An illustrated journey that attempts to answer these questions and more!
http://www.exploratorium.edu/learning_studio/auroras/
 

Earth’s Magnetosphere:

Exploration of the Earth's Magnetosphere: Detailed information on the Earths magnetic environment and the physics behind it.
http://www-spof.gsfc.nasa.gov/Education/Intro.html