License Plate Games
Instruct everyone in the car to look at the letters on passing car's license plates and attempt to make up a phrase. Begin each word of your phrase with a letter from the plate. The first person to make up a phrase using letters from a license plate wins the round.
Another option is to identify as many different state license plates as you can.
Counting Game
Pick an object that you want to count. Make sure it is something that is common enough that you will see it over and over on the car ride. Examples of common objects are mailboxes, speed limit signs or a certain color vehicle. Count the objects silently on your side of the vehicle only. Whoever has the highest number of objects counted by the next time the car stops wins.
Journaling Activity
Buy each passenger a journal or create your own out of notebook paper and yarn. Write descriptions of interesting landmarks or destinations as you encounter them. Cut pictures out of old magazines to match your descriptions and glue them to the appropriate page of the journal, or collect a small souvenir and glue it to the page. Another alternative is to give each passenger a disposable camera to take pictures of each noteworthy spot.
Arts and Crafts Boxes
Supply a sturdy box with a lid for each child. Paint the top of each lid with black or green chalkboard paint and allow to dry. Load each box with an equal type and amount of arts and crafts supplies such as chalk and erasers, paper, glue sticks, safety scissors, yarn, shaky eyes, construction paper, stickers, stencils, washable markers, mini dry-erase boards and erasers and old magazines. When a child becomes bored, instruct her to draw on the top of the box with chalk or create something artistic with the supplies in the box.
Team Storytelling or Sing-a Longs
Engage in team storytelling. Choose a person to begin by making up the first sentence to a story. The next person has to add a sentence to continue the story and so on until no one can think of anything else to say.
Sing-a-longs can be set to family favorites on your car's CD player or each person can choose a song and everyone can take a turn singing a line until the song is complete.
Window Art
Allow children to draw pictures on the windows of the car with washable markers. Supply them with a cotton cloth to erase the marks. Kids can also play simple games such as tic-tac-toe on the window as a fun alternative to paper.