I have a pair of noise canceling headphones from Sony. I found them to be the best buy for the price. These headphones can get fairly expensive, some nearly the cost of a new computer. This pair has functioned very well, the battery life is long and they are relatively compact.
I can't fly without them anymore. We are constantly bombarded by noise in our daily lives, and flying is a social overload. These could also be used at the office, or at home, to tune out unwanted distractions in our daily lives. (I once used them while they were jack-hammering the concrete next door!)
Noise canceling headphones work in two ways: First, the simple part; most of them are closed ear design, meaning they physically block the sound by covering your entire ear.. The manufacturers even use special sound-obsorbing foam to keep out even more external noise.
The second half of canceling noise is a little more high tech. A small microphone and speaker mimic the exact sound coming from outside the headphones. Two identical sound-waves that point towards each other cancel each other out!