Google Maps added a new feature that can predict traffic information, based on past conditions for any day of the week & time. If you click on the Traffic button in a supported area from the US, Google Maps shows real-time traffic information. "Comprehensive traffic data is available in over 30 major US metropolitan areas (including Los Angeles, New York, Chicago, and others), with partial coverage available in many more," according to Google Maps help center. There's also a traffic layer in Google Earth and Google Maps Mobile, but these applications don't include yet traffic prediction.
Google Maps, Navigation, Traffic, New Features, Google