One of the powerful features that was introduced in the Virtual Earth APIs in version 3.0 is the GeoRSS Layer.  The GeoRSS Layer allows you to easily add a set of points and information to the map from a standard GeoRSS XML file using the W3C Basic Geo (WGS84 lat/long) Vocabulary or the GeoRSS Simple Syntax

For example, here's a link to a GeoRSS file showing the tracking information of Hurricane Ivan from 2004:

http://krkinnan.members.winisp.net/georss/2004hurricaneivan.xml

Using the Layer API with a GeoRSS file, you can easily create a mashup with a few lines of code presenting this information.  This can be done with the VELayerSpecification object and the AddLayer call on the map.  The VELayerSpecification defines the layer and the AddLayer call adds the layer to the map.  Once you have created a map and loaded it, the following code shows how to add a GeoRSS layer to the map:

var layerSpec = new VELayerSpecification();
layerSpec.Type = VELayerType.GeoRSS;
layerSpec.ID = "Ivan";
layerSpec.IconUrl = "
http://krkinnan.members.winisp.net/i/hurricane01.gif";
layerSpec.LayerSource =  "http://krkinnan.members.winisp.net/georss/2004hurricaneivan.xml";
layerSpec.Method = "get";

map.AddLayer(layerSpec);

The mashup when created will show the items as a series of points.  When hovering the mouse over the points, a pop-up will appear with the information related to that point:

Click Here to see a live demo of this mashup.

For more information regarding the Virtual Earth API and using GeoRSS Layers, see the Virtual Earth Interactive SDK.