PBS
Pbs: Mathline: Let's Face It [Pdf]
Check out this math project about polyhedra! Students will enjoy the hands-on activity while they learn about tetrahedrons, hexahedrons, octahedrons, dodecahedrons, and icosahedrons. [Requires Adobe Reader.]
National Council of Teachers of Mathematics
Nctm: Illuminations: Volume of a Cube
"The volume of a cube can be developed by considering unit cubes, a single row (longs) of unit cubes or a single layer (flats) of cubes using this applet." This easy software makes it possible to easily construct a cube and take it...
University of Cambridge
University of Cambridge: Nrich: Building With Solid Shapes
Predict which solid shape constructions would be unstable as shown at this one page website. Solutions are available right at the website.