Gephi - Gephi is an open-source software for visualizing and analyzing large networks graphs.
Pajek - Pajek is a lightweight solution developed from scratch by an extraordinary team of developers for the purpose of Large Network Analysis.
SocNetV - Social Network Visualizer (SocNetV) is a cross-platform, user-friendly free software application for social network analysis and...
Centrifuge - Centrifuge is a complex and highly useful data analysis tool that allows for interactive data exploration.
Graphviz - Graphviz is open source graph visualization software. It has several main graph layout programs.
KeyLines - The JavaScript toolkit for graph visualization