Often times the entertainment in the air will help you pass the time.

If you are into music, often times there are a lot of different channels of music and talk shows as well.

I carry my laptop everywhere, so I record my journal / thoughts when I fly (it's a great time for personal reflection).

I also play electronic chess to keep the mind sharp.

Just think about what you like to do on the ground, and see if you can do the same on the air to pass the time.

Also, it doesn't hurt to being writing a Trip Report so you can let us know how your trip was (and your relatives who are dying to hear the scoop).