Android: Many countries are unsupported by Google Maps Navigation, even if Google has the information to support them. With the Google Maps Ownhere mod, you can unlock navigation in those areas, whether you’re visiting or you live there.
The mod is available at the XDA Forums, and you’ll need to back up your Google Maps and Street View installations using an app like previously mentioned Titanium Backup before uninstalling them and loading the mod. Once loaded, restore the backups and reinstall Google Maps, and the app should be unlocked.
You’ll know it worked if Google Maps launches after the reinstall. There’s a more extensive how-to at the XDA Forums, along with download links for the mod.