OpenStreetMap is a free editable map of the whole world. It is made by people like you.
OpenStreetMap allows you to view, edit and use geographical data in a collaborative way from anywhere on Earth.
And you can use their maps in NavIt!
You will need to do the following :
Grab a map from OpenStreetMap :
Of course, adjust the bbox to the area you want to grab. Use a small area, or the grab may fail.
Once you have the map.osm, parse it. There is a script for that in the navit/src/script folder.
navit/src/script/osm2navit < map.osm > mymap.txt
Now add a map source to your navit.xml :
<map type="textfile" enabled="yes" data="/path/to/mymap.txt" />
And navit will now be able to read your OSM maps.
Note that since September 2007, NavIt is provided with a demo map of München.