One app that is great and even plenty of iPhone owners use is Google Maps. There are plenty of great features on it, such as estimated time of arrivals and road congestion updates. I even noticed this weekend that when looking at my hotel on Google Maps, it shows the date that I have a reservation. I believe it synced because I had the reservation on Google Calendar.
Google Maps us great because you don't have to pay for updates. I believe all of the mapping will be important for Google's self driving car.