I recently finished developing JusticeMap.org. I have created a set of around twenty open map layers for the US for income and race, based on Census data.
I created a set of map tiles using TileMill. Race is available at the county, census tract, block group and census block level. Income is available at the county and census tract levels.
I also created a set of kml files. When the user zooms in to zoom level 15, they transition from using map tiles to displaying kml (this allows them to zoom in as far as they like - without creating 10 TB of map tiles).
You can view the data at my website. Or you can also add the layers to your own map using javascript. You can also download the layers.
I want to help people make maps and would be happy to assist in using these layers!
Where can I promote this service? Is there a community of people creating open map layers like this?