For a route like this I'll use Google Maps to get a rough idea of via points. However, rather than using the bicycling instructions, I'll typically use the automobile ones with a setting of "avoid highways". That keeps me off the largest interstate highways at least in the East. I'll then also bring along some state maps and adjust things as appropriate based on how the trip is going and local information I hear along the way. I've sometimes also gone to a site like "motelguide.com" and found towns likely to have motels.

This Google map gives an idea: http://maps.google.com/maps/ms?ie=UT...76e818304d&z=6 I wasn't 100% certain where I was staying or route choices but had done enough in advance to mark potential stopping points. On this trip I was doing it as a motel trip. Each morning I then figured out the specific possibilities and had two or three choices. My most likely one might have been 64 miles away, but if things were going well, perhaps there was one at 89 miles or alternately one at 45 miles...