A hit a small snag today when trying to rename an XCode project.
Pro tip: Don't change the name of your XCode project from anywhere outside of XCode.
Apparently XCode has some magic behind the scenes when it renames a project, which probably changes some references to the project internally. If you rename your project file from outside of XCode you will no longer be able to run your project.
To rename the project from within XCode, simply click on the project from the file view in the XCode IDE, and it will allow you to change the name, and additionally will give you the option to save a snapshot of the change in case you want to roll back.