This is an interesting map of the political campaign contributions from companies in the oil & gas industries to politicians who are candidates for the US federal office. This is a relationship map of the contribution network and therefore, the icons for the companies and candidates are placed so that they are as close as possible to whomever they contribute to or receive contributions from.The tool allows users to not only see the oil contribution network for the 2008 US Presidential Race, but also from 2000 and 2004, where George W. Bush's dense network of nodes is impressive.
For more information on how the graphs are generated there's a FAQ page with further details.