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. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proc. First International Conference on Semantics And Digital Media Technology (SAMT), volume 4306 of LNCS, page 56-70. Heidelberg, Springer, (December 2006)
F. Mitzlaff, D. Benz, G. Stumme, and A. Hotho. HT '10: Proceedings of the 21st ACM Conference on Hypertext and Hypermedia, page 265--270. New York, NY, USA, ACM, (2010)
M. Grahl, A. Hotho, and G. Stumme. Workshop Proceedings of Lernen - Wissensentdeckung - Adaptivität (LWA 2007), page 50-54. Martin-Luther-Universität Halle-Wittenberg, (September 2007)
N. Du, B. Wu, X. Pei, B. Wang, and L. Xu. WebKDD/SNA-KDD '07: Proceedings of the 9th WebKDD and 1st SNA-KDD 2007 workshop on Web mining and social network analysis, page 16--25. New York, NY, USA, ACM, (2007)
G. Flake, S. Lawrence, and C. Giles. KDD '00: Proceedings of the sixth ACM SIGKDD international conference on Knowledge discovery and data mining, page 150--160. New York, NY, USA, ACM Press, (2000)