One of the many new features of Oracle MapViewer 11g (which is now in the final testing stage) is heat maps. If you don't know what exactly is a heat map, it is a color based 2D representation of a point data set's distribution pattern. It is great at revealing clusters of points or events that occur in a study region.
The above map displays the CITIES table in MapViewer's MVDEMO data set as a heat map. The color gradients (from white to green to orange and finally to red) shows the distribution pattern (clusters) of cities and towns of US. In MapViewer terms, the CITIES theme is rendered using a HEAT MAP style. Internal tests have shown MapViewer can easily generate a heat map from hundreds of thousands of points, on the fly.
Here is another screen shot, this time showing the distribution of pizza restaurants across the states.