Gephi is the leading visualization and exploration software for all kinds of graphs and networks. Gephi is open-source and free.
GEXF (Graph Exchange XML Format), language for describing complex networks structures, their associated data and dynamics.
Graphlytic is powered with the world's leading graph database Neo4J which enables us to give you fantastic performance
NodeXL is an Excel 2007/2010/2013 template for viewing network graphs, with a set of .NET Framework 3.5 class libraries that can be used to add network graphs