All alternatives for offline GPS navigation are expensive. Google Maps is doing quite well, but can’t compete with present solutions and dedicated GPS devices, such as Sygic, Garmin, TomTom or … CoPilot. The last one mentioned can be used for free as of right now.
The free version of CoPilot was released especially for mapping and planning but I think it can very easily be used for navigation. It’s praised initiative by ALK Technologies and want to benefit from the growing number of such solutions and from other developers. For Android, download the application on the Play Store for iOS it’s available through iTunes.
You can read the official press release here.