Mapquest offers an "avoid highways" map filter, but I find that the best way to make it work to a bikers satisfaction is to build certain waypoints in along the way to ensure that you take the most scenic route, so it requires some manual attention for best results. You can also look at satellite imagery of the route to get a birds eye lay of the land in advance of the trip...
Luckily there's a chain of educational supply store here that have a "map world" section. I can get maps of any area. The maps that the US Geological Survey has show the roads. that you won't see on other maps because these maps are smaller scale. These maps are being upgraded by means of satellite mapping. You can get maps for any area of the USA you want by going to http://topomaps.usgs.gov/.
Remember, a paper map will always work and can't be rendered useless by dropping it or by a dead battery.
When I was in NC I used DeLorme's Gazeeter, which can be found in most bookstores. It's the same size and thickness of a road atlas, but only focuses on one state. Once you use it a few times for exploring, you'll get a good feel for what roads on the maps are good in real life.
They make them for every state and are only a few bucks (5 or 8) so over time you could build quite a collection. Don't waste your time on Illinois, though. It looks like they just bound grid paper together and threw some rivers on. Sigh.
I second the point to advrider.com. There are some serious GPS gurus over there, and could really help you out, particluarly if you're into unimproved and gravel roads. It's a great community site (and the only one I frequest other than here). I post under Savoir-Faire.
For my last trip, I just got on the Interstate long enough to get to a Visitor's Center (usually the first exit) and "collect" one of each state's free maps. MO, AR, and TN is good, NC is good, the GA map is surprisingly crappy and only marginally accurate, FL map was exceptional.
Don't bother with any of the generic maps. Not very motorcycle oriented. The Delorme Atlas & Gazetteers are great. I've used them extensively. They're 99% accurate, and the detail is is very high. The pages are oversize and back cover is a map of the state, with a grid laid over it with 1" square boxes. Each box is a FULL page in the book. THAT'S detail.