NBC Weather Plus has integrated some seriously slick weather tracking data with Microsoft Virtual Earth. The site uses Adobe Flash to render Virtual Earth tiles, then overlays rasterized, opaque weather tiles to visualize weather around the US. In fact, if you try to navigate out of the US it will stop you - yes, I tried that. :)
You can view the weather on an aerial or cartographic map; adjust the transparency of the weather; quickly zoom to a national view; or view the spotlight (my fav). The spotlight focuses on a particular city - today was Phoenix, AZ. I assume that has something to do with the fact that it's 77 degrees there today (February). Yeah, it's raining and 45 today in Seattle.
I also found their Local Weather Search to be useful.
You can enter any address, city, postal, whatever and get the forecast, but also radar and temperature maps (sadly, not using Virtual Earth) and cameras. A video played and I thought, "Now, this is cool! Local video from the NBC affiliate in San Diego (KNSD)," but my hopes were dashed when it was just a nationwide broadcast. But, alas it was just a usability issue! There are tabs for radar, video and cams. The video tab brought me to a piped in feed of weather on a map - I was really hoping for some actual footage from the newscast. Perhaps Lorrie Jordan (fellow Aztec Alumni) giving the weekend forecast? Feature request. Oddly, I saw Lorrie on The Ellen Degeneres show moving like she did at house parties at State (yeah, we partied) and couldn't, for the life of me, figure out why. I digress.
NBC Weather Plus - another successful and awesome Virtual Earth implementation!