When going out with a group of photographers, it's always nice to have a theme, like "everything red" or "things in motion". Let's collect a few suggestions here as answers to this question. Don't forget to vote!
Planning a road-trip is very different from other route-planning. Setting stops and breaks, deviation from the initially planned way etc. If, which tools are you using for this, which on- or offline maps and other software are helpful for you?