Not all guilds have an active thread here on the forums, but here’s a list of those who do, in no particular order:
Order of Oronaar
Ardent Pursuit
Dustpaw Caravan
Dirge of Teldrassil
Boulderhelm Brigade
Shadowbane Coven
Painted Shields
BOOMTEC
Grim Gest
Chosen of Draenor
Guilds who dont have a thread here:
House Bemoux
Red Venturers
Hand of Conquest
Ronin