Dallas to the Panhandle
This is a really long drive, until you compare it to the drive to Big Bend. Then, it's not so bad. It is one of the few routes that is not covered by Interstates. (If you really want to use the Interstates, you can take I-35E north into Oklahoma, and then take I-40 west.)
There are a lot of small towns to visit, so it is an interesting route. You can see the town where Bob Wills originated (and he is still the King.)