Nav4All is free and works pretty well. No maps display, but the nice features are that it turns off the screen when you have several miles to travel (saves battery) and turns back on when you are a mile or so from the next turn. It also supports bluetooth audio, so when I ride my motorcycle, the audio ports into my bluetooth helmet headset and I can hear the directions.
I also use the Garmin software, which seems to be more accurate than Nav4All. It's not free and doesn't support BT audio, but is a good piece of software.
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