V-Trafic is an amazing Google Maps mash-up showing current traffic conditions for the whole of France.
V-Trafic is able to show traffic conditions throughout France by aggregating traffic data collected in real time by an incredible number of sources. Just to show how many sources they are using I'll list them:
Motorways: APRR (société des Autoroutes Paris-Rhin-Rhône), AREA (société des Autoroutes Rhône-Alpes), ASF (Autoroutes du Sud de la France), ESCOTA (Société des Autoroutes Estérel, Côte d'Azur, Provence et Alpes), SANEF (Société des Autoroutes du Nord et de l'Est de la France) - SAPN (Société des Autoroutes Paris-Normandie) - ATMB (Autoroutes du Tunnel du Mont-Blanc), SFTRF (Société concessionnaire du Tunnel Alpin du Fréjus et de l'Autoroute de la Maurienne A43), Cofiroute.
Regional: The SISER (Interdepartmental Service of Security and Operations of the Road), Coraly covers Lyon
Urban: The city of Paris measures real-time traffic on its entire network. The system consists of electromagnetic loops buried in the pavement and measures the flow of vehicles. Taxi G7: Since 1996, a fleet of 4400 taxis have been equipped with satellite tracking to monitor the movement of each car. Analysis of the taxis' position with proprietary algorithms, enables the density of traffic to be calculated.
National: - The CRICR (information collected on the ground by the police).
Now that's a lot of sources, so I'm guessing V-Trafic's information is fairly accurate.
The current conditions are shown on the map by coloured polylines. It is also possible to turn on and off a number of layers to see road works, accidents and events that may cause road closures / delays.
As well as showing real-time traffic conditions V-Trafic can also show you the current weather conditions anywhere in France, Velib stations in Paris (bike rentals) and parking spaces in Paris. If you are living in France I recommend you bookmark this site now - you are going to be using this a lot!