Chemical manufacturing company WACKER CHEMIE announced in their Q2 report that they have developed a method of 3D printing with silicone. The process uses a custom designed printing program that applies very small dots of a special silicone material to a glass printing bed. The layer of silicone i then vulcanized using a UV light that cross links the silicone molecules into an elastomeric material. You can find out more about the process over on 3DPrint.com.