An interactive simulation of Earth's seasonal dynamics that includes the axial tilt and other aspects of Earth's annual cycle.

This is part of a larger lab from the University of Nebraska at Lincoln: http://astro.unl.edu/naap/motion1/motion1.html

This short video, adapted from NOVA, explains how Earth's position relative to the Sun might be responsible for the dramatic shift in the climate of what is now the Saharan nation of Djibouti.