The ultimate in personal fabbing is "rapid prototyping" (3D printing). Formerly the methods used for rapid prototyping were confined to making models out of fragile plastic or wax or corn-starch, but the past few years have seen new methods that allow printing directly in metal, with companies like ProMetal, EOS, MCP, and Optomec making tools that can take a CAD file and print out a solid object in steel, aluminum, bronze, titanium, or any number of other metals and alloys. Some produce porous models (sometimes 40% air), others make solid parts. Either way, it's a big step towards building anything you want from the ground up.

Technologies such as this (Selective Laser Sintering) are also relevant to green manufacturing because they're additive processes, not subtractive ones, so there is almost no waste -- instead of having a big block of metal and milling away most of it into scrap, a part is built one layer at a time from metal-dust fused to the metal below, and the dust that isn't used for this part will be used for the next. The dust itself even holds the part up, no secondary scaffolding material is used. ...The process is still quite energy-intensive, however.