Clustered view of search results on map

Looking at the global solidarity economy map ( http://www.essglobal.info/mapping.html ), if you do a search (choose "Brasil" for example, and then a number of sectors fields), the results are returned on the map via a colored, circular "epicenter" representation, with the number of initiatives written inside the circle. This is a very nice way to display a large number of listings in a small space, and makes the map look very powerful. Is this possible for us to do with openstreetmaps? The clustered view is nice, and straightforward to do with Google Maps. With OpenLayers, clustering is also possible, but would probably take more work to make pretty [2,3]. [2] http://openlayers.org/dev/examples/strategy-cluster.html
[3] http://stackoverflow.com/questions/6641919/openlayers-nice-marker-clustering