Science U
Science U: Reasons for the Seasons
This webpage uses diagrams and video to explain the causes of the seasons.
Other
Lunar and Planetary Institute: Sky Tellers: Myths, Magic, Mysteries of Universe
Very nice website with excellent graphics depicting the change of the seasons and how the seasons are different between the northern and southern hemisphere. Also has a nice informational table of the spring and fall equinox and summer...
Ohio State University
Beyond Penguins and Polar Bears: Common Misconceptions About Day and Night
Misconceptions about the causes of seasons and day and night are common through all ages. Use the information on this site to help your students understand these concepts. Included are links to many resources and lesson plans for...