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...
A. Borodin, G. Roberts, J. Rosenthal, und P. Tsaparas. Proceedings of the 10th international conference on World Wide Web, Seite 415--429. New York, NY, USA, ACM Press, (2001)