handsonmath.com (Popularity: )
http://www.handsonmath.com/ Geometric model building courses to improve understanding of geometry, using a Matrix kit for sale on the site that can ...
polyhedra.mathmos.net (Popularity: )
http://polyhedra.mathmos.net/ An online encyclopedia of the shapes, including ray-traces and other data on the Platonic Solids, Kepler-Poinsot Polyhedra, and Archimedean Solids.