Most prominent this value shows up in the comment copyright header when you create a new file in Xcode4.
1. Click on your project root in the Project Navigator on the left.
2. Enable your Utilities view on the right while the project root is marked.
3. Select the File Inspector. To make sure you are in the right location, the Identity should display your Project Name.
4. Under Project Document is a text field called Organization. Enter here the Organization name you want to show up for all your new files that get generated in this project.
That's it. Let me know if you have any problems or comments.