This is very cool (to me at least).

It is all of the animated radar data across the entire United States from the National Weather Service mosaiced into one large animated image. You can see the outline of every county!

The small radar images you usually get on the web always bug me because I always seem to end up wanting to see what is just beyond where the radar data stops. This certainly takes care of that.

It is large, about 2 megabytes, and it is updated about every 10 minutes.