Placebook [geographics.cz] aims to provide a visual overview on how Facebook users are distributed around the world. As a unique feature, any Facebook users can log into the system, in order to receive a map and all relational statistics about their own personal friend network.
The map has been designed in the typical Facebook blue style, and includes a small data graphics dashboard showing the absolute counts of users per country, the proportion of users within a population, and the distribution per age group. Not surprisingly, this project was the 2010 winner of the NACIS Student Web Mapping Competition.
See also Mapping Facebook Connections and Project Palantir.