Scholastic
Scholastic: Dirtmeister's Science Lab: Let the Sun Shine In
Students graph data reflecting time of day and length of shadow, and then draw conclusions about Earth's seasons and position in relation to the Sun.
National Geographic
National Geographic: A Reason for the Season
This site provides a learning activity that can be adapted for all age levels that deals with the seasons. Students are asked to become a "season sleuth" and discover what causes the seasons to change.