While the new system launches March 3rd, I had a chance to preview it at beta.healthycity.org.
I searched the Iron Triangle neighborhood in Richmond, CA, using zip code 94801. I selected environmental facilities and health clinics, then added asthma rates to produce this map:
I know the map is hard to read, but there are some nice features, such as the ability to redefine shading colors and breaks in quintiles. One can add a range of demographic, housing, economic and health data. One major piece that I couldn't find was an an export function that would allow for more complex comparative analyses using statistical software. Yet, one great feature is that everything is geocoded with Lat/Long coordinates, so hopefully eventually exporting into GIS, Google Earth or some other mapping program should be seamless. This project is very similar to InfoShare, http://www.infoshare.org/, in New York City, which I have used for many years. The interface with Healthy City is much more user friendly, but with any data and mapping portal, it will take you some time to get exactly what you are looking for.