Every day we see new types of 3D printers, as well as materials to print with. Today Disney Research and CMU unveiled a felting printer, which 3D prints wool into any given shape desired. The felting printer works just like an FDM printer in that it prints layer upon layer of a material (In this case wool yarn) until a final object is completed.
http://3dprint.com/2861/3d-felting-printer/
Researchers are now working on ways to integrate hard materials, within and attached to, the soft felt-like material being printed. Check out a quick video of the printer below to better understand how it functions: