The January 2010 issue of Physics Today’s web watch section mentioned the Sun|trek web site which contains a number of resource for learning about the Sun and it’s effect on the Earth.  The material is varied and the comment about being "devoted to teaching schoolchildren" is a bit vague on the age group, but the format includes a large number of images and other materials that make it engaging, certainly for middle school and possibly for older elementary students (depending on the lesson).  Of course, some of the material is clearly targetted at high school students, so you’ll need to poke around a bit to find material.

References to grade level appear to be based on the British system (things like "KS3" and "year 7"), but you can figure it out.  I’m a little disappointed with the cool-looking cartoon summaries don’t have entire cartoons sequences to go with them.  A few years back, I bought and handed out copies of a booklet called "Cycles" from the Astronomical Society of the Pacific.  I really thought I was going to get something like that, or like the Cartoon Guide to Physics (link is to Harper-Collins, the publisher; you can buy from your favorite bookseller).