HeadPhone.com has a lot of info on...headphones.  Duh.  Ok, it sounds obvious, but they really do have some good info if you're in the market.  A section I really found useful were headphones specifically intended for work.  And there are differences.

They have a lot of info for things such as company contact information, returns, repairs, warranty info, manuals, etc.  And of course they have a lot of technical info on all the headphones.  Enjoy

View all the headphone info here