Bring on the snacks. As adults know all too well, eating gives you something to do. Be careful, though -- getting your kids sugared up may backfire. Pack some healthy fare, and don't worry about them turning up their noses at it.
Beat the boredom. Be sure to load some kid favorites onto your iPod or take some of your child's CDs. Portable DVD players can be a lifesaver, too. New DVDs they haven't seen are a bonus. Kids often have a hard time with headphones, though, so make sure they're comfortable before you go, and have at least one backup pair.
Get in the backseat. A little face-to-face contact, some patty-cake, and a few tickling games go a long way toward distracting a cranky baby or a bored toddler.
Try to tune out the tears. There may come a point where no amount of singing, snacking, or engaging will do -- your child wants out of the car, now. How to deal? If your child isn't hungry or wet, remind yourself that he's safe in the car and won't die from crying. Eventually, he'll stop or fall asleep.
Choose travel toys wisely. Rivoli has had luck with magnetic and Aquadoodle boards. And she suggests that you find a local grocery store or pharmacy if your toy stash grows stale. "It's likely they'll have an inexpensive selection of things your toddler hasn't seen before."