I am pretty serious about my audio and have done a lot of reading on this topic. I only once tried the BOSE noise cancelling headphones on a AA flight but my problem is the size of them (too big for light travel), the shells (they sit on your ear so you can't sleep), and the high price (300$).

I have just bought a pair of Shure E2c in-ear phones. They don't have any noise cancelling technology but are basically earbuds that have a small pipe run through them that brings in the sound. So the earbuds seal off most of the outside noise. I tried them long haul and just loved them (the only annoying thing was the stewardess who kept on asking me questions! I had to keep taking them out as you will have a very hard time hearing anybody talk to you).

Shure has very high quality earphones. I got the E2c which are about 55 GBP. One step up are the E3c which is the US are about three times that I think but apparently are even more amazing sound wise.

I wasn't too bothered as on a plane, listening to mp3's you are not going to feel like there is a little angel pissing on your ear anyway! But on a train you get pretty close to it. Walking through Waterloo station during rush hour or sitting in a crowded BA lounge with the music on is pretty surreal - so quiet!

Now these headphones do take a little to get used to (different size buds etc and you need to get comfortable getting them in). In ear canal phones might sounds a little freaky but if you are OK wearing normal earbuds then this is nothing strange. Do a search on google as there are lots of reviews on these.

www.shure.com/earphones/eseries_e2c.asp