I suggest the KNIME free software with the DBSCan Cluster Algorithm, by Martin Ester, Hans-Peter Kriegel, Joerg Sander, Xiaowei Xu: A Density-Based Algorithm for Discovering Clusters in Large Spatial Databases with Noise.
I use Geokettle ( http://www.spatialytics.org/projects/geokettle/ ) as ETL geospatial tool. You can know about it in OSGeo Live CD http://www.spatialytics.org/projects/geokettle/