The Sun's rotation generates huge magnetic fields which shape active regions, sunspots and sculpt massive loops and prominences. The Sun is a magnetic, variable star...

http://wwwssl.msfc.nasa.gov/ssl/pad/solar/the_key.htm
Magnetism: The Key to Understanding the Sun: They have good background on magnetism.

http://www-spof.gsfc.nasa.gov/Education/Intro.html
NASA/GSFC Exploration of the Earth's Magnetosphere: The site to visit for a wealth of information on Earth's magnetosphere. Excellent historic information.

http://www.agu.org/sci_soc/cowley.html
A Beginner's Guide to the Earth's Magnetosphere: Good easy-to-understand information.

http://www.spacescience.org/SWOP/
Space Science Institute "Space Weather" Center: Terrific graphics and plenty of information on the Sun. Be sure to visit the Classroom Resources section.