The biggest weather site on the web just lauched with Virtual Earth as their mapping platform of choice. Here's a sample: http://www.weather.com/weather/local/92123.
The site using a Flash interface to overlay weather data atop of VE. You can see different types of overlays such as radar, clouds, clouds and radar or turn off the weather feed altoghether just by clicking a radio button. You can alter the transparency of the weather overlay by using an opacity control ranging from 0 (no transparency) to 100 (no data). The app also shows animation of weather patterns. I was watching an 8 hour time lapse of cloud movement starting this morning @ 1AM. You can also step through the animation or pause it at any point. They have a neat transition for zooming too. You can double click to zoom anywhere on the map and the map will recenter than shoot you down.
Virtual Earth had been buried on the weather.com web site, but not you can access it from the home page by entering your postal code. Sick, sick, sick!