Must have collection of broken glass textures ready to be used in your Photoshop manipulations. This list contains free broken glass texture, cracked glass texture, broken window texture and so on. If you need other types of glass check this list 50 Free Glass Textures for graphic designers.
You can use a broken glass texture to create a broken glass brush for Photoshop. Or you can use the broken glass texture to create a grungy old look effect.