Do you know how to have a nice clustering in OpenLayers such as this google example ?
I have just implemented a so called AnimatedCluster strategy for OpenLayers. You can see a bit more about it at: http://www.acuriousanimal.com/2012/08/19/animated-marker-cluster-strategy-for-openlayers.html
It is only a firts version but adds a nice animation to the clusters. There are many things to improve but it is a starting point.