Visualization of graph data is incredibly challenging, particularly when it comes to extremely large, scale-free graphs and social networks. A few simple searches on the Web and you will find some mesmerizing and very cool images. Perhaps the most cited...
S. Staab, J. Angele, S. Decker, A. Hotho, A. Maedche, H. Schnurr, R. Studer, and Y. Sure. AAAI 2000/IAAI 2000 - Proceedings of the 17th National Conference on Artificial Intelligence and 12th Innovative Applications of Artificial Intelligence Conference, Austin/TX, USA, July 30-August 3, 2000, AAAI Press/MIT Press, (2000)