OpenStreetMap
From GeoWiki
OpenStreetMap creates and provides free geographic data such as street maps to anyone who wants them.
The project was started because most maps you think of as free actually have legal or technical restrictions on their use, holding back people from using them in creative, productive, or unexpected ways.
One benefits of OSM is that there are pre-built maps for some GPSr units that are updated frequently.
There are daily builds of OSM maps of Australia for Garmin GPSr units available at these sites:
