I must be missing something obvious, but I can\'t figure out how to rename my project in Xcode 4.
If I remember correctly Xcode 3 had a dedicated menu item for this
In addition to renaming the project, you may want rename the scheme so that it matches your new project name.

To change the name of your scheme:
Product ==> Manage Schemes...
Then select your scheme and hit return/enter to edit the name.
Alternatively, Product ==> New Scheme... to create a new one with your new name :)