I travel a lot. As such, I never go anywhere - even at home - without the traffic feature enabled on my Google Maps app. When you enable traffic on your Google Maps app, you get pretty much real time data from all the suckers who are signed into google in your metroplex.
Basically, Google monitors all those phones on the road, determines how much density there is and how slow/fast they are moving and delivers a color systems to show you what you are looking at. Picture of the grid to the right (enable photos on your screen or click through), here's what the colors mean:
Green - your commute is going to go great, my friend.
Yellow - it's a little congested, like your 4 year old nephew who can never seem to shake his head cold, even in the summer...
Red - Abandon hope. Ye are screwed.
The map to the right is Atlanta. The Kinetix offices are at the top of the map, at the junction of 285 and 400. I was coming to that intersection and saw a sea of red between me and Birmingham (my destination). I actually went other way around the outer beltway - which doubled my milage but saved me 15 minutes.
Only in the ATL. But I wouldn't have know the real time situation without traffic-enabled Google Maps.
Use it if you like being in the know. Go to the menu of your Google Maps app and simply hit "Traffic"