Two nice Java libraries for visualizing and exploring graphs (networks)

1. Prefuse (http://prefuse.org/)
2. JUNG (http://jung.sourceforge.net/)

Main observation:

• JUNG is designed for graphs, while Prefuse is designed for many different types of data (which include graphs).
• JUNG has graph operations and algorithms that Prefuse doesn't have
  
• JUNG seems to be better documented
• JUNG seems to be more scalable
• Examples from Prefuse seem to be more pretty
• Prefuse provides nice interactivity and cool animations