This is an interface for doing global or US comparisons of different indicators. Military spending, IKEA, Number of Gold Medals, Crops, Energy, are just some of the indicators that can be mapped.
Do you like some of the New York Times maps and graphics? If so, you can view some of the projects here. Also, at the bottom of the page is MapShaper, which looks like it could be very useful for simplifying shapefiles for KML use.
My impression of this site is "Data 2.0." I like that the data is organized by category, you can upload and download data, and it has graphing capabilities. It could be a little stronger on the mapping aspects, but if you find the data you are looking for here then it is worth it. Also, there may be social aspects to this site that I have not explored yet. Similar to the geocommons finder without the mapping component.