I've previously mentioned another web site for walkers (click here), WeekendWalk.com. In a recent posting on this site, the author Paul Schneider discusses a foot-powered visit to Big Bend National Park in Texas with his father.
You don't have to go to Texas or the West Coast to plan a walking trip. Look for areas where small towns are relatively close to each other, and where the roads have wide shoulders (or there are hiking paths off the roads). And where there are places for you to stay. Cape Cod, the Eastern Shore of Virginia, the Upper Potomac, and the Massachusetts and New Hampshire coasts are just few of the places that might be walkable.