Keeping the kid(s) occupied

So when you're in for a long car ride or plane ride, how do you keep your kids occupied?  Of course, there's the ever-popular DVD player, but are there any other creative (or not-so-creative) options out there?  We haven't purchased a portable DVD player yet.  We're hoping to never have to resort to that option.  It's partly out of principle, but mostly out of practicality.  I mean, if the DVD player doesn't entertain the kid, what option do you have after that?  At least for our family, the DVD player is the nuclear option - there's no going back, and if it fails, I'm not sure there are any options left for keeping the kid entertained.  So we've been utilizing low-tech solutions so far, starting small so that we can work our way up to the nuclear option if absolutely necessary.  For those of you with kids with eczema - it's like starting with the lowest steroid cream (hydrocortisone) to see if that can get rid of those itchy red bumps, and then working your way up to the stronger steroid creams.

Anyway.  One thing that our son really likes is the Aquadoodle Travel Doodle.  I found it at Target on clearance in the summer, and my son loves it.  It's simple, compact, and there's no mess.  It can keep him occupied for quite a while.  Also found at Target on clearance were Travel Tangoes.  I haven't yet introduced them to my son yet, since he's still a little young for them, but I'm hoping they'll keep him occupied and silent when he's a little older.  He also loves books, so we make sure to go to the library to get him new books to read (though if you're worried about losing these library books, you can always bring books you have at home already or purchase books at a garage sale or book sale and keep them hidden until you plan to be sequestered in a cramped space with a young child.  We've also tried getting books on CD from the library.  The kid wasn't too interested in them - I think he was a bit too young and certainly couldn't follow along in the book, since he can't read yet.

Another tip is novelty.  To make sure that a toy will keep my child's interest for at least a small amount of time, I make sure to keep some toys as only travel toys.  He doesn't get to play with the Aquadoodle at home, thus ensuring that it will be a new fun toy for him to play with whenever he gets to play with it.  I've also tried wrapping up some of his more regular toys - the whole process of unwrapping the toy not only takes time, but also seems to make the familiar toy more interesting.  Get new books from the library.  Or when you see something on clearance at the store (even the dollar store) and have an upcoming trip planned, don't give it to the kid right away, but save it for the trip.

What are your tips for keeping a kid occupied during travel?