Check out this article on the mini metal maker at 3ders.org. It's an FDM printer that extrudes a metal paste - metal powder with an organic binding - that you then fire in a kiln, ending up with a metal piece. They're aiming this printer at the jewelry-maker market. Print resolution is about the same as a run-of-the-mill FDM printer at 450 microns but they're trying to get it down to 200 microns.

From the looks of things, they've taken the idea of a clay extruder, which has been around for a while, and married it with readily available metal clays like this silver clay from ebay.

It would theoretically be possible to build your own by building a standard reprap, building and installing this paste extruder from thingiverse and loading it with metal clay (although I understand the consistency of the clay needs tweaking).