Foam

Insulation Foam Board (Seen in the first 9 images) - Can be used for creating molds and is an inexpensive material for low budget prototyping.
Preferred method is to use actual Tooling Board Renshap 460. Check out the "Modeling Foam" Link to see parts machined from Renshape 440

Zotefoams Plastazote. This foam is a closed cell nitrogen- charged cross linked polyethylene foam that has increased tear strength while being lightweight. This foam is available in almost any color. This foam is an excellent choice for case inserts and tool kits as it is impervious to most chemicals.

Components below were machined for the creation of molds for the Power Industry and Tool Control for various industries.