I know it came out last year but I have just discovered BikeHub.
BikeHub is a great FREE android app (also for iPhone) that finds a cycle route for you, then gives you the option to follow it using your phone’s GPS. It will also give voice directions and vibration alerts when coming to turns.
This screenshot is from the desktop version which gives you an idea of some of it’s features.
All I need now is a handlebar holder for my Dell Streak 5. Might this be another job for duck tape?!