So, I wanted to create a thread to consolidate all the subclasses we know about, and a brief description of them. I plan on keeping this updated, but I'll rely on you all to give me links to sources I may have missed.
EDIT: $2.8m stretch goal is adding a 3rd sublcass to each core class. So, I am adding spaces accordingly. Even though Priests and Paladins are using Deity and Order as their subclasses I'm still adding a 3rd slot to them for the time being.
Barbarian
1) Corpse Eater is one subclass for the Barbarian.
2)
3)
Chanter
1) Beckoner is the subclass focused on summon