Platform Specific Resources
There is a convention established by the old Apple YellowBox whereby the resource locating system in NSBundle would look for resources with the pattern name-platform.extension, where platform could be "winnt" or "windows".
Cocotron continues with this convention, implementing a general way to specify platform specific resources. So, for example you could have MainMenu-windows.nib for the Windows version and just MainMenu.nib for OSX. Or Localized-linux.strings for your Linux version. There is "windows", "linux" and "solaris" defined for the three platforms.