Xcode - deactivate automatic updates (documentation)
From SnOwy - Ed's Wiki Notebook
This hint is for xcode running on Mac OS X.
I've found out that Xcode steals a lot of bandwidth -- when it does this, it's actually downloading documentation.
If you run a webserver or have a limit on your bandwidth per month -- this can be very disadvantageous.
Some support found at one of Apple's users' forums -- turn off its automatic updating under preferences -> documentation. It's in an unfortunately obscure location.
A screen capture of the pertinent preferences under Xcode -- Uncheck the highlighted text box and it won't download additional updates without you manually checking. You might have to log out and back in again.

