The iPod / iPhone "Maps" app is pretty efficient. It will even find business locations and navigate a route for you. I use Google Earth a fair amount for navigation too. Zoom in and find highways, interchanges, towns.
ANY map, route planner software will find the "road most traveled." The H-D Ride Planner has the option of staying off the main highways. Of course if you have a specific route in mind, you'll need to specify waypoints at every route option. Otherwise you get directed toward "the main highway."
If I'm headed somewhere I'm not familiar, I use several map sources. Google Earth allows you to get 360 degree street-level views of the area on a lot of routes. (Click on the "camera" icon . . . ) I've used the street-level view option on Google Earth to find gates, trail heads, off road entries when out with the 4WD. On the scooter, it's a useful tool to get down on the road and have a look at the condition of the pavement, terrain, features "in town" -- Crystal Springs, Nevada at the Junction of 375 and 318 looks like it might be a reliable stop-over for food/gas. In fact it's barely more than a ghost town, and the street level feature tips you off to that.