Year after year, Apple falls further behind Android on the navigation front. Although iPhone 4S users can ask Siri for directions, they still can’t get voice-guided turn-by-turn navigation like Android users can. Until native maps navigation arrives on the iPhone, MapQuest will have to suffice. Unlike competing apps from TomTom and Garmin, MapQuest is free, and it includes some helpful features such as traffic, walking directions and a low battery mode.
Link: MapQuest 4 Mobile