Shows the basics of Discontinuous Cartogram using SLD.
This is a map of percentage unemployment in 2000 from the US Census. It uses a discontinuous cartogram to help direct the users eye to more populous areas. See here for more details of how it is done.
To do this you will need this jar and GeoServer 2.1-beta (or later). Just drop the jar in to the WEB-INF/lib directory and restart.