Although some pretty impressive stuff is coming out on CSS3, there still seems to be some Adobe Flash applications to discover, particularly these powerful weather maps.
WeatherSpark allows for an animated weather radar with 6 hours of history.
Special thanks to Jonathan Voigt for Buzzing this one. Apparently Wunderground (Weather Underground) is another similar app.
If you have an Android device, I recommend playing around with the Rainy Days app.