One of the limitations of 3D printing is in the materials -- plastic might be the most affordable and widely available, but it's also cheap and brittle. So some students at Michigan Tech University have made a relatively cheap metal 3D printer, and they're releasing the plans to the masses.
The team's printer was cobbled together for under $US1500. It required a small commercial MIG welder and an open-source microcontroller to lay down thin sheets of metal on top of one another to create jewellery-like objects in little geometric shapes.
Now, this 3D printer might be cheaper than a MakerBot Replicator 2, but it's also a hell of a lot more dangerous. So it's something that's intended for a skilled metalworker or perhaps a machinist, rather than your standard basic 3D printing hobbyist. Think more an aid group in Haiti 3D-printing medical supplies or a small manufacturing outfit than your weird neighbour 3D printing holiday ornaments.