Heatmaps provide a clear visual display of densities of features for easier analysis:

• ​http://www.sethoscope.net/heatmap/
  • Python toolkit, featured in ​http://www.slideshare.net/abeusher/heatmaps-are-the-heat
• ​AcidMaps: GeoServer plugin to work with WMS
• ​http://blog.felipebarriga.cl/programacion/openstreetmap-heatmap-using-openlayers/
  • ​http://blog.felipebarriga.cl/olheatmap_demo/
• ​ATMs in Beacon Hill, Boston
• ​Clickmaps
• ​gHeat - heatmaps for Google Maps
• ​OpenLayers' Cluster Strategy (which we already use)
  • Examples:
    • ​http://openflights.org/blog/2009/10/21/customized-openlayers-cluster-strategies/
    • ​http://www.erepat.com/