I added a video for my favorite weather widget. The HTC weather app is a port from the app you see on the HTC Android phones. It has a very cool look to it. You can also download additional skins. The stock skin is by far the best looking.
They also added a separate clock to the 2.3 version. The clock also has a few skins built in.
The app requires .Net 4 and only runs on Windows 7 or Vista. You can also download a portable version which is much easier than worrying about the .NET versions. The weather source is MSN, Foreca or FreeMeteo.
Some sample screen shots