More WX 411 than you'll ever be able to use
If you're a WX junkie like me, this is the Mother Lode. It's a compendium of every cool weather site, courtesy of the Airline Dispatchers Federation. These are the folks who tell the commercial air carriers where to go and when to go there, and they know their stuff.
The whole plethera of info can be found here. A few jewels from their page is the National Airspace Status (NAS) info, a Quick Brief page that will give you a "right now" look at US weather, a National Overview with a collection of very high quality images, and if you really REALLY need to know what is going on in Madagascar, yes, you can get that info here too courtesy of the World Nexrad RADAR images offered from Weathermatrix.net on the ADF site.