Chris Harrison's Digg Rings visualization plots the top 10 most-dugg stories by days of the week May 24, 2007 to May 23, 2008 (bottom) and all stories (close up) Dec. 1, 2004 to May 23, 2008 (top) rendered as a series of tree-ring-like visualizations moving outward in time.
Visualization by Chris Harrison, Carnegie Mellon University, Editor-in-Chief of the ACM student magazine XRDS, http://xrds.acm.org.
Early patterns of Digg diggs and YouTube views reflect long-term user interest.