Google Maps is probably the most complete mapping app for mobile phones...
Navigation apps for iPhone sorted by popularity
Trapster is a crowdsourced app to report hazards or accidents on the road
- Sygic: GPS Navigation, Free Offline Maps, Route Directions, POI & Traffic, Speed cameras & Head up D FREE
A turn-by-turn GPS navigation app with hundreds of high quality maps...
- Citymapper - New York, Washington DC, Boston, London, Paris, Berlin, Madrid, Barcelona - the Ultimat FREE
Comprehensive urban travel tool, making cities easier to use