A pretty cool online tool to browse academic publication networks and communities and to see relationships between individual researchers has been provided by Microsoft Academic Resrearch: http://academic.research.microsoft.com/VisualExplorer#3616114
They provide textual search as well as a very advanced visual explorer enabling you to access Co-Author Graphs, Co-Author Paths and Citation Graphs.
Very nice even for just playing around a little bit.
Publication Network Visualisation by Microsoft Academic Research