Each of my kids has a backpack which we fill with an assortment of "goodies" for each long trip. Items vary according to individual taste and age, but they include things like new books, colored pencils (less messy than markers) and paper, magnetic bingo, small stuffed animals, finger puppets, puzzle books (sudoku, crossword, mazes, etc), sticker books, wiki stix, old favorite books... and we allow short sessions of gameboy play for kids over five. We have thus far resisted getting a dvd player for the car. I worry that they'd never look out the window and see where we are if we had a movie playing.
We also listen to audio books. We go through the entire LOTR about every other year. We also have The Odyssey, some Mark Twain, and several children's tales by Odds Bodkin and Jim Weiss. Most libraries have audio books too, and we borrow for something fresh.
