OKAY as far as I am aware, residents of Castle Summers are:

Buffy Summers
Dawn Summers
Xander Harris
James T. Kirk
Leonard "Bones" McCoy
Dean Winchester
Sam Winchester
Tara Maclay (HAHA)

Also just temporarily, I believe Fred Burkle and Cordelia Chase are staying there, because of Angelus on the loose. Buffy is attempting to persuade Giles to live there too, but she hasn't broken his will yet. I don't think I missed anyone? >_>