My parents used to let me pick out two activity books that they would buy for me before any major road trip. I usually picked a logic puzzle book and a coloring book. One time, I picked out a pair of "things to do in the car" books for kids, which turned out to be too easy and too boring. However, I did glean a few good family car games, one of which my brother and I still play to this day.
Here's how it works. One person starts by reading a word from any object outside the car. Usually, this is a billboard. "Money!" The next person has to find a word that starts with the last letter of the first word. "Yamaha!" "Anyone!" "Exit!" "Turn!"
This might sound extremely easy, but finding Yamaha took me almost fifteen minutes. (Note: to keep the game moving, you are not allowed to pass up a word in hopes of finding a better one.) Of course, we live in Chicago, so any road trip we take requires traversing through a chunk of the Midwest. I don't know if you've ever driven through the Midwest, but it's mostly flat and corn and trees and some more corn. There isn't even that much other traffic, so you shouldn't hold your breath waiting for a Yukon to drive by.
My least favorite letter to get stuck with from this trip? 'K.' My brother would look at billboards like the ones pictured above and choose "network" instead of "now." And I would sigh and watch all those pretty Wisconsin license plates fly by and wish that he was slightly less smart.
I tried this game indoors once when my friends and I were stuck at an airport for countless hours, waiting for someone's plane to arrive. It was difficult and fun for a while . . . until we found three words that looped (e.g. turn, nice, exit) and got too lazy to do anything but repeat them.
Anyway, I dare you to try this with a sibling or a friend on your next road trip. It's guaranteed to stave off boredom for at least five minutes. You'll have to come up with your own games after that.