Pepakura is a great little program to view 3D models and print patterns. Also, if you have the designer version, you can make papercraft from any 3D model that you have.
Pepakura files end in .pdo, so you at least need the (FREE) viewer to open them.
(I'll write something eventually)
Unfolding a 3D Model
(Someone knowledgable write a guide here)