Just a shout out, Google map navigation originally on Android 2.0 now on 1.5, i.e. G1 and others..
Unfortunatly not on 1.6 (Sprint Hero & G2 (HTC Hero)). but news says G2 eventually moving to android 2.0..!
P.S. Google Map Navigation has voice prompts etc, just like the garmin/tom tom, and its free..!