Simulations
These sites have simulations for many physics principles. They are interactive and some are animated. Examples are, Kepler's law animation, and electric field mapping.
http://www.walter-fendt.de/ph14e/ Walter Fendt
Good variety arranged by topic
http://www.falstad.com/mathphysics.html Excellent wave simulations
Good graphics and 3D Visiualizations
http://webphysics.davidson.edu/Applets/Applets.html Davidson College
Resource page for "Physlets"
http://physics-animations.com/ Good variety arranged by topic
http://www.cornerstonesd.ca/~gfkells/Physlets/ Index Page of simulations
http://www2.swgc.mun.ca/physics/physlets.html Good variety arranged by topic
http://www.phy.ntnu.edu.tw/ntnujava/ Simulatations from a Chinese Physics Forum
Many excellent simulations by Fu-Kwun Hwang
Good variety arranged by topic
http://www.sciencejoywagon.com/physicszone// The Physics Zone
http://qbx6.ltu.edu/s_schneider/physlets/main/index.shtml Dr. Scott's Physlets
Good variety arranged by topic