I have tried paper maps, Google maps, Mapquest and the "Map My Ride" website. So far I have not found any really good way to figure out good routes. All of the above will leave out perfectly good paved roads and more to the point a lot of them will try to send me down gravel roads on my road bike with 700Cx23 tires. Google maps seems to be particularly bad about this. Google also claims they have their bike route maps in beta testing but the product has a ways to go to be very useful. I usually have to torture their mapping routine to get a good route in areas that I know what the roads are like.
In my area Mapquest seems to be the best of the lot although they don't show every paved road.
Map my ride ends up being mostly a big klunky website that is an enormous memory hog and unless somebody has already published routes in your area does not provide much useful new information.
Rand McNally and other paper maps don't usually have much information on the scale that cyclists need. On a state map you end up trying to map your route in an area the size of a few postage stamps.
Back in my college days, (more than a few years ago) I collected county maps that were printed on legal pad sized paper that would show every paved road in the county. Sadly those maps seem to be a thing of the past.
So what do you use to figure out new routes to try on your bicycle?