Dr. Stewart Silling has provided me with a copy of his talk on Peridynamic theory that he presented at McMat 2007.  The PDF file of the talk is attached below.

In order to deal with classical material models and volume constraints, Dr. Silling has modified the original theory to allow for forces that are not necessarily pairwise. A bit on that is included in the talk.

You can find more information on peridynamics including a bit on Dr. Silling's code (EMU) at  http://www.sandia.gov/emu/emu.htm (though it's slightly out of date).  Dr. Silling promises to update the site in the near future.