I just became aware of a fairly new social network for Duraspace, the parent organization of the Fedora, DSpace, and Mulgara projects.  They're using a Crowdvine site at: 

http://duraspace.crowdvine.com/

Looking over the list of current active members it looks like all the major players in DSPace and Fedora are already there.  Of particular interest was the "Solutions Communities" tab which they describe as:

"DuraSpace Solution Communities are made up of individuals that have gathered around specific areas of interest. These communities work to find and share resources to advance the knowlege base available for the group or anyone with an interest."