Researchers at Michigan Technological University have created a plastic extruder, called Filabot, that turns home recyclables into usable filament for 3D printing. Basically the machine takes 4-inch pieces of plastic and shreds them, before melting the plastic and extruding it through changeable nozzles, and shaping it for use in printers. Filabot works with thermoplastics like HDPE, LDPE, ABS, and NYLON, though PVC is out because of, you know, serious toxicity risks and stuff. The group calculated that Filabot uses a tenth of the energy needed to recycle empty bottles to produce its filament.
The first model, the Filabot Reclaimer, is in production now. The unassembled Filabot sold on Kickstarter for $350 so pricing will probably be in that range. This thing could really be worth it for avid 3D printers, and could drive down costs for hackerspaces and other groups. More here.