The parts on the printer I use are made of ABS plastic, like Leno's example. You can vary the densisty to control material use... from solid to a lighter honeycomb. They're atually quite strong. I'm soon to receive a version of the printer that uses a "water soluble" support material, meaning that when your part is complete, you drop it in water and it dissolves the support material (necessary for most part configurations) away. This allows for more intriciate, delicate, or interlocking parts. The parts are accurate to +/- .010". My current machine has a maximum size of 10"x10"x12", the new water soluble machine is 8"x8"x10" maxiumum.
If someone wants to make a part, let me know. There is some cost for the material, but it works well for part development. Once you've developed all the final features and dimensions of the part, you can either use the ABS plastic part that has printed, or send the electronic part file to a CNC shop for production of a metal part.