Key Links:
Transmog
Holy
Discipline
Shadow
Weak Auras/Macros/UI stuff
Legion PoV Videos
Priest Discord
If you have any suggestions on stuff you would like to see or stuff that you've felt has been lacking in the past in regards to guides and readily accessible information please feel free to reply here and I'm sure everyone will do their best to scrap something together.
EDIT: @Atonement wrote up a really great FAQ for disc priests, new and returning so be sure to check it out. You can find it here.