Via the VE Blog:
You can now view animated radar and cloud cover maps at Weather.com, built on the Virtual Earth platform. You can select what you want overlaid on the map and set the level of transparency. You can also animate the imagery over the trailing hour with the controls below the map.
There is a little more information about the application in the "What is this" link above the map.
Tease: Watch this space for some exciting developments around VE for our partner community.