Google announced a new feature of Google Maps Navigation (Beta) which now routes you around traffic.
From the announcement: "So we’re happy to announce that Google Maps Navigation (Beta) will now automatically route you around traffic. With more than 35 million miles driven by Navigation users every day, this should add up to quite a bit of time saved! […] You don’t have to do anything to be routed around traffic; just start Navigation like you normally would, either from the Navigation app or from within Google Maps. […] Starting today, our routing algorithms will also apply our knowledge of current and historical traffic to select the fastest route from those alternates."