Learn how to make costume armor and props using foam,
plastic styrene sheeting, and other materials
BioWeapons.com - Advice on making molded, "organic-type" armor
Studio Creations - Hi-impact armor, props. Focus on vacu-forming, latex.
Sculptor.org - Links to Moldmaking tutorials and suppliers.
Claystation.com - Techniques Guide to mold making and slip casting.
Jongleur's Working with Polymer Clay Tutorial - Good advice on clay sculpting
Getting Started with Molding and Casting - A short beginner's casting guide.
Hirst Arts Fantasy Architecture Moldmaking Guide - This website has a decent sculpting tutorial as well as moldmaking supplies.
Smooth-On - Suppliers of resins, plastics, latex, foams - offers starter kits and has a "how-to" section.
The Compleat Sculptor - (No that wasn't a misspelling.) Offers lots of different kinds of sculpting tools and supplies, including hard to find Friendly Plastic pellets...