After discussing methods of creating custom circuit boards to use with are Arduino projects, and Mr Jagoutz suggest Fritzing - Designing PCB's on the computer and then sending the files away for printing. Mr Jagoutz also recounted an anecdote from his youth in which he and some of his pears would make circuit board via an acid etching process. I remember reading about conductive 3D printing filament. Here is a link to a product that I found:

http://www.makergeeks.com/coabs3dfi10.html