If you don't have a replacable derailleur hanger, you can use one of these:
http://www.biketoolsetc.com/index.cg...-Inserts&q=&s=
Scroll down to items 17 and 18 depending on how thick your dropout is. You will need a 15/32" drill bit to clean up the damaged threads and allow the Dropout Saver to fit. You can buy one of these locally or Bike Tools has them too:
http://www.biketoolsetc.com/index.cg...id=WB-DS/DRILL