A zoomable treemap of the Chicago Data Portal, with the datasets grouped by categories (defined by the portal) and dimensions drawn based on the size of the individual datasets. Currently the color simply helps keep the rectangles distinct, but in future versions information (e.g. # of views the dataset has received, or tags from the portal) could be encoded in a color scale. The rectangles are linked to the datasets they represent in the portal (just click anywhere within the rectangle).
The d3 code is heavily based on code shared by The Ohio State University Department of Political Science