In XCode 4, open up your project. Select the top-most item in the Project Navigator (MyProjectName, 1 target, iOS SDK 4.3 -- or whatever). Open up the file inspector (View->Utilities). In the Project Document section, you should see an "Organization" line. Edit that, and new files that you create will display the new organization name. This is a project setting, hence you'll have to do it for every project. You'll have to search-and-replace to fix up any existing files.
For new projects that you create, the Organization Name will be whatever the value was on the previously open project. (You can edit it when creating the new project.)
If the Organization Name entry in the UI is blank (and for your very first project ever in XCode maybe?) it'll pull the business name from the "Me" card in your address book.
