It is believed that Perfect/Absolute pitch cannot be developed (a gift you either have or don't), but who really knows...all things are possible...However, Relative Pitch can be developed through practice and ear training.
I illuded to this in another post, but most are under the impression that perfect pitch is just being able to recognize a note without hearing a relative note, it actually more of being able to recognize the "frequency" of a note with no other reference...for example if an instrument was out of tune, sure someone with relative pitch may be able to recogize it was out of tune, but they most likely could not get those notes to the exact frequency they need to be for the instrument to be in perfect tune.