the Sun Doing Lately http://www.lmsal.com/YPOP/Spotlight/Today/
From the Yohkoh Mission Public Outreach Page: Information about and views of the sun in different wavelengths of light.
You See What I See? http://www.lmsal.com/YPOP/Classroom/Lessons/Filters/
From the Yohkoh Mission Public Outreach Page: A lesson about astronomical imaging using different color filters.
Sun, A Pictorial Introduction
From the High Altitude Observatory, (http://www.hao.ucar.edu/) a division of the National Center for Atmospheric Research. This collection of slides serves as an excellent introduction to the study of the sun, however the text is written at a college level. Here is an easy lesson with which you can adapt the slide show for a middle or high school classroom.