Explain 3D is a site that offers a collection of 3D animations of simple machines. The animations use the Unity web player which enables viewers to zoom-in, zoom-out, and rotate animations 360 degrees. Recently Explain 3D made all of the animations available for free. In addition to the animations of simple machines like elevators and hand pumps, Explain 3D now offers 3D models of the universe and electrical systems.
Applications for Education
Explain 3D could be a good source of models to include as part of a larger lesson that you're constructing for your students to view online. To get the most out of the models your students will probably need you to explain what is happening and or the connections to the larger lesson.