Gephi is an interactive visualization and exploration platform for all kinds of networks and complex systems, dynamic and hierarchical graphs.
Exploratory Data Analysis: intuition-oriented analysis by networks manipulations in real time.
Link Analysis: revealing the underlying structures of associations between objects, in particular in scale-free networks.
Social Network Analysis: easy creation of social data connectors to map community organizations and small-world networks.
Biological Network analysis: representing patterns of biological data.
Poster creation: scientific work promotion with hi-quality printable maps.
Runs on Windows, Linux and Mac OS X. Gephi is open-source and free.