FAART
Fans of An Absolutely Remarkable Thing. You can join by clicking here.

NERDFIGHTERIA
The unofficial Nerdfighteria Discord server. You can join by clicking here. Loosely affiliated with Eff Yeah Nerdfighters.

TUATARIA
Tuataria is a community of "cyber sleuths" that came to be when John Green announced a scavenger hunt before the release of his book Turtles All The Way Down. It exists mainly on Discord, with three main servers: Tuataria, Hogwartaria (the Harry Potter roleplay server), and Bibliotaria (for everything books). You can join by clicking the link attached here. The Tuataria Book Club is available here.

LIFE'S LIBRARY
The official Discord discussion groups can be joined by clicking here.