Gephi
"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.

(www.gephi.org)

It has decent poster-size pdf output for poster presentations and such.. nice for academia.

http://gephi.org/users/download/
http://gephi.org/users/install/#linux
(after unzipping, you can for example mv your folder to /opt/)