Here's the Bose QC-25 - the most famous of the noise cancelers I think. And it's extremely good at canceling noise, with a couple minor caveats. From what I hear with this headphone, they managed to not only be the best at noise cancellation, but they produced a near-perfect audiophile signature at the same time. I can't say that all aspects of the sound quality are audiophile-grade, but listening to many very familiar music tracks, the details were present and the tone qualities seemed correct. The build quality is luxurious, and if the QC-25 proves to be durable, the $300 USD price tag seems like a good value. In the picture links I included, you'll be able to see the major differences between the Active mode and Passive mode signatures.
http://www.hifiheadphones.co.uk/forum/showthread.php?t=4209