produces the most commonly used set of maps, you can also go to America By Bike
and view the routes that they use.
Are you planning on doing a self-supported tour, ie camping out most nights, cooking your own meals, generally living off what you carry, or are you planning on doing what is usually called "credit-card touring" (I'm not really crazy about that name, but it's the one that's usually used), where you will be staying in motels, eating in resturants for most, if not all, meals. CCT generally lets you cover more miles per day, simply due to the fact that your not lugging as much gear around. That really helps determine what kind of bike would be best suited for the trip. People have done Long Distance Touring on everything from fixed geared bikes to Mountain Bikes to Recumbants. Most folks here would say that if your going to tour, a touring bike is the best bet. Generally speaking, think long wheelbase, relaxed angles, LOW gears, and stable as a rock. As for me, I ride a dedicated touring bike (C-dale T800 Silk Tour), and on an extended trip, will generally spend 5 days riding and camping, and then a day off with a motel room. I do like my occasional creature comforts.
America By Bike does fully supported tours (They haul all your stuff, set up rest areas, motel and resturant), they do the northern tier route in 50 days, the Adventure Cycling tour that is comperable is fully self supported (camping each nite, and tour members take turns cooking), takes 90 days. I'm just posting those so that you get a feel for the times you might need.
I recommend Crazy Guy On A Bike
and read some of the travelogs posted there. Good tool to get an idea what other folks have done.
Hope this helps, there is a lot of experence in this forum, so don't hesitate to ask,
Who has been fighting flu all weekend