I’ve mentioned various communities online, such as the ones centered around making movie prop replicas or building Halloween prop displays, where you can find a plethora of prop-building tips and techniques. Cosplay is another such community.
Cosplay means dressing up and role-playing as fictional characters. It’s most popular in Japan, with cosplayers dressing as anime characters. However, it is also present throughout the world and involves characters from science-fiction, fantasy, and history as well. It can be extended to Renaissance Faire participants, or even Civil War reenacters.
As such, websites focused on these communities have a plethora of information on making DIY armor, swords, and other weapons.
Here is a collection of props and armor tutorials from one such forum. There are tutorials on working in fiberglass, polystyrene, foam, and vinyl.
Cosplay.com has another thread collecting various prop and costume tutorials on working with certain materials or building specific items.
The Prop Blog, by Amethyst Angel, showcases her work, tutorials, news, and information. It’s also a huge gateway to a number of similar cosplay sites and showcases around the internet.