I originally tried to use the MarkerClusterer from Google but that didn't work because at the closest zoom level the pins directly on top of each other weren't

I originally tried to use the MarkerClusterer from Google but that didn't work because at the closest zoom level the pins directly on top of each other weren't clickable. The Spiderfier is much better suited for this problem (lots of people geocoded with the same city, state, or other location name).