On a more practical note... most airport bookstores have inexpensive maps of the country you may be most likely to fly over. Some passengers (pax in airline parlance) enjoy following their progress during the flight... assuming you have acess to a window seat. Additionally, when walking through airports I now see kiosks that rent DVD movies and portable DVD players. They appear to be fairly reasonable in price. This should be good for two hours or so of entertainment...
Read. I finished all six Winston Churchill book on WW2 on one project I worked on commuting between Asia and South America. I looked like an airline seat.
Sleeping and reading a good book. I flew lots for the last 2 months of last year and initially spent an absolute fortune on magazines and newspapers.
I then bought a good book or two and read them while on the flights and they made the journeys hugely more enjoyable.
If I were going on holiday then I'd now definitely take Clanad's advice and get a map or city guide.