Reasons for the Seasons

http://astro.unl.edu/naap/motion1/animations/seasons_ecliptic.swf
Interactive Simulation of Seasons (better one)

http://highered.mcgraw-hill.com/sites/007299181x/student_view0/chapter2/seasons_interactive.html
Interactive Simulation

http://education.nationalgeographic.com/education/activity/the-reason-for-the-seasons/?ar_a=1

For the Reasons for the Seasons Investigations