Hexagonal binning layout in d3.js

2000 random (though centrally-skewed) data-points plotted atop a uniform hexagonal grid or lattice

the same points above binned to hexagons and represented proportionally

using a 9-class choropleth scheme to represent the point density by hexagon

a bit of redundant symbolization, as both color/value and size represent the point density. Either size or color could alternatively represent another attribute

a value-by-alpha hexgrid of point density atop a Google hybrid map