I need to create a range-graded circle proportional map, i.e., a map that has circles overlaying a map the size of which circles indicates the proportional density of what I'm trying to measure. This is best understood by example, and can be seen here: http://www.d.umn.edu/geog/cartfolder/HTML%20Pages/Map-Types.htm. I've tried poking around with Google Maps API, and can't find anything that will let me create proportional circles on top of a map display; and, furthermore, I would like to be able to narrow it down by major cities in the U.S. (SF, LA, NYC, Chicago, Dallas, etc.).
Is this even possible?