For noise canceling in my sound proof recording studio I use Studio Kans.
http://www.indoorstorm.com/Studio_Ka...nes-p-549.html

But for video work I use the Sony 7506 pack great and nice sound.

I worked with a guy who had a pair of noise cancelling phones about 11 years ago. It was a fairly quiet office, but there were about 10 computers, A/C, copies, printers, laser fax with fans in it, etc. They seemed decent, but I can imagine them working better on lower frequencies because it's easier to reproduce lower frequencies with cheap microphones. The highs are more difficult. :)

The 7506's are great. I've been wearing a pair for the past 6 hours watching tutorials and things. They're a little head fatiguing at first, but once you get used to them, they're nice.