One drawback to Google Maps — and presumably to the other mapping services — is that while it’s easy to map points and lines (“polylines”), mapping regions (“polygons”) is something altogether different. And that makes it rather difficult to do species range maps or choropleth maps in a map mashup (though it occurs to me that you could import certain shapes as overlays). Beginning Google Maps (see previous entry) examines this question by showing how to process shapefile data into XML.