Five years ago I spent a summer in doing research at the University of Georgia. I'm from California, where between the months of May and September, it basically doesn't rain. The hills turn brown and by early October wildfires start popping up all over the state, and really, the whole west. In Georgia in the summer, it rains. It rains quite often, in fact. There were thunderstorms nearly every afternoon.
It was in Georgia that I learned of the utility of the best weather site on the internet, wunderground.com. Their best feature, was, and still is, doppler radar that updates every six minutes when there's rain. Five years ago all the other websites I searched updated the radar no more quickly than every half hour. In Georgia I would often log onto the website to see if I could dodge between thunderstorms and walk to the Physics building, or go for a bike ride. The radar was accurate and current enough to do this.
In the five years since the radar has just gotten better. Now you can zoom in, make animations, and use many other cool tools. Since I'm a paying customer (I believe it's $10/year, and highly worth it) I get no advertisements and expanded radar tools.
Below is an example animation, fresh off the presses for today. It's Saturday morning, a time when I usually go for a bike ride. In fact, the sun was out this morning when I woke up. But my trusty wunderground.com weather page told me that I'd better wait. I live just a bit north of the black cross with a circle around it, which you can see is about to get pummeled by some thick rain.
The other, more popular weather websites have gotten better in the last five years, too. However, I still think that wunderground.com is still the best by far.