Ekisto, by visual artist Alex Dragulescu, is an experiment in visualizing online communities that provides an interesting city effect. So far there are views for StackOverflow, Github, and Friendfeed.
A graph layout algorithm arranges users in 2D space based on their similarity. Cosine similarity is computed based on the users' network (Friendfeed), collaborate, watch, fork and follow relationships (Github), or based on the tags of posts contributed by users (StackOverflow). The height of each user represents the normalized value of the user's Pagerank (Github, Friendfeed) or their reputation points (StackOverflow).
Also available in print.