Gephi is the leading open-source platform for visualizing and manipulating large graphs.
Fast Powered by a built-in OpenGL engine, Gephi is able to push the envelope with very large networks. Visualize networks up to a million elements. All actions (e.g. layout, filter, drag) run in real-time.
Simple Easy to install and get started. An UI that is centered around the visualization. Like Photoshop™ for graphs.