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

* http://www.slideshare.net/abeusher/heatmaps-are-the-heat
 * Summary presentation from SOTM-US 2012
* http://www.sethoscope.net/heatmap/
 * Python toolkit, which works well with !OpenStreetMap
* http://jjguy.com/heatmap/
 * Pyython toolkit using PIL
* [http://acidmaps.org AcidMaps]: !GeoServer plugin to work with WMS
* http://blog.felipebarriga.cl/programacion/openstreetmap-heatmap-using-openlayers/
 * http://blog.felipebarriga.cl/olheatmap_demo/
* [http://boston.povo.com/Beacon_Hill?heatmap&radius=GreaterBoston&tags=atm ATMs in Beacon Hill, Boston]
* [http://blog.corunet.com/the-definitive-heatmap/ Clickmaps]
* [http://code.google.com/p/gheat/ gHeat] - heatmaps for Google Maps
* [http://dev.openlayers.org/releases/OpenLayers-2.9.1/examples/strategy-cluster.html OpenLayers' Cluster Strategy] (which we already use)
 * Examples:
  * http://openflights.org/blog/2009/10/21/customized-openlayers-cluster-strategies/
  * http://www.erepat.com/