With data straight from the National Weather Service, Wunderground.com is one of the sites I use constantly when creating my own weather forecasts. The site is fast and cleanly laid out and includes basic radar data, hazardous weather outlooks, and more. Block forecasts for every three-hours with specific chances of rain are also very nice. However, the site lacks some of more detailed maps that can be found on Intellicast or the National Weather Service's own website.

Works best for me. Putting in a city name immediately brings up a comprehensive page of data, intelligently organized. That page also includes quick links to the other most used pages, such as tropical weather.