The Weather Channel
WeatherNet From the University of Michigan One of the earliest (and still one of the best) weather sites on the web.
StormTrack Storm Chaser Homepage
Al Pietrych's Weather Web (Tons of data, divided by state/region)
The Storms Prediction Center The National Severe Storms Laboratory
The Alaska Climate Research Center (Yay!)
Brian's Wild and Wacky Weather Oddities and Fun
Brian's Weather Galleries