[sorkvir]

I think that the regional Diplo centers are:

New Targonor
Bordinar's Cleft
Leth Nurae
Khal
Ahgram
Pankor Zhi
Tanvu
Caial Brael
Martok

Not too sure on that. The item itself is easy to use. When you see the area's name appear on your screen, right click on it and it gives you the faction.

edit: based off Aruspex's post below. Changed Hathor Zhi to Pankor Zhi