My work colleagues and I have been having a discussion about doctors (we work in healthcare), and we're split down the middle as to whether a specialist doctor would have a speciality, or a specialty (no "i"). Is there a specific use for each word, or can they be interchanged?
It's standard US medical editing practice to change instances of "specialities" to "specialties." Note the certifying agency: American Board of Medical Specialties.
There's a good explanation of the difference here.
In addition to the regional differences among English-speaking nations, it points out that 'specialty' is more commonly used as an adjective; 'speciality' as a noun.
As a native speaker of British English, this is the distinction I make.