NavStarter is a application (including desktop widget) to enter addresses (with history support and contacts lookup for suggestion) and start navigation using Google Maps navigation.
Precondition is that you have installed the patched maps.apk with navigation, see http://2030.tk/wiki/Google_Maps_Navigation for more information and links to the XDA thread about this.

This is the donate version, see http://2030.tk/link/navstarter for a free download of this application.

Screenshots: