This project at Washington State University is incredibly nifty. Researchers use a 3-D printer to make a bone-like material that can temporarily do the job of bone, while serving as a scaffold for new bone to grow on. Over time, it dissolves safely.
Read more about it on the WSU website
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.