Last May I did an abbreviated version of my Dunbar Number talk at MeshForum 2006. A MP3 podcast of that talk is now available at IT Conversations  or can be downloaded here (10mb). If you'd like to follow along, here is a pdf copy of my presentation sides (10mb). Biggest addition to what I've written about before is some discussion about different kinds of social software and what what size groups they seem to be appropriate for.