ClassFlow
Class Flow: Nets
[Free Registration/Login Required] In this flipchart, students explore geometric sense by interacting with plane diagrams that create a three-dimensional shape.
Wolfram Research
Wolfram Math World: Net
Here you can find a definition for the mathmatical term 'net', in addition to a couple of examples.
National Council of Teachers of Mathematics
The Math Forum: Pictures of Icosahedrons
This site from Dr. Math and the Math Forum provides several links to pictures of icosahedrons. The information is somewhat brief, but worth checking out for a background on the subject.