For long-haul flights, I carry on in my Mandarina Duck bag:

Bose QC2 noise-cancelling headphones, and ear plugs - very effective when used together.

Sony Hi-MD Walkman. I've not yet converted to an iPOD as I like to use Minidiscs for recording. I have MDs of music compilations of different genres (house, chillout, soul/groove) for different moods and also recordings from BBC Radio, including the Essential Selection and Essential Mix from BBC Radio 1 (now, incidentally, available in the US on Sirius) and various talk shows from BBC Radio 4.

A copy of The Economist (usually two weeks old).

Another magazine, probably one of The New Yorker, Vanity Fair, Travel & Leisure or Dwell.

A book. Preferably one that's light, breezy, and I'm already into - such as Martin Lukes - Who Moved My Blackberry?

A change of clothes, just in case checked baggage goes missing.

My own in-flight amenity kit consisting of aspirin, anti-bacterial wipes, lip-balm, toothbrush and toothpaste.

A bottle of water and maybe some fruit.

Photocopies of passport, itineries, lists of phone numbers etc - just in case I lose anything.

Most importantly a notebook and a pen. When I'm travelling, I'm always noting - for writing reviews of airlines or hotels, potential places to see, purchases etc.