weatherbug

Weatherbug is a free weather client that sits neatly in your taskbar and gives you a lot of weather related information. On the bar, it displays the current tempature for your area. Also, in the event of severe weather, it will chirp at you, and flash the little bug icon over the tempature ont he task bar. While the map isn't as great as what you can get on weather.com, it's still a really good desktop weather client.

It is also avaliable for the MAC, and can even be intergrated into CAMTWIST as an overlay, to give the current tempature on live video streams.