Material Choices

In Plastics:
ABS
Acetal
Acrylic
Delrin
HDPE
Nylon
Polycarbonate
PVC
Teflon
Urethane

And more…

For an excellent guide to plastic properties,
check out: http://sdplastics.com/

Foam:
Butter-Board
Model-Board
EPS Foam

Woods:
Balsa
Oak
Any other, but close-grain woods mill best

Metal:
Aluminum
Brass
Copper
Also Available:
Ceramic, Wax and Rubber!