Besides the Dragonmarked Houses themselves, there are a number of Guilds in Eberron:
Esoteric Order of Aureon – The oldest Circle of Wizards in Breland.
The Twelve – The Twelve is an alliance of wizards sponsored by the Dragonmarked Houses.
Guild of Starlight and Shadows – a Guild of Wizardry and Sorcery in Breland.
Healers Guild – an institute run by House Jorasco
Raincallers Guild – provides weather-manipulation services for agriculture and is an institute of House Lyrandar.
Windwrights Guild – dominates the shipping trade of Khorvaire and is an institute of House Lyrandar
The Clifftop Guild – an Adventurer’s Guild located on the Upper Dura, in Sharn, Breland.
The Deathgate Guild – an Adventurer’s Guild located on Middle Tavick’s Landing in Sharn, Breland.
Finders Guild – primarily composed of House Tharashk members, but it also includes many independent inquisitives, bounty hunters, explorers, and prospectors.
The Diggers Union – For over a century, this semi-independent organization has supplied treasure hunters and adventurers to Morgrave University and its affiliates for various special projects.
The Closed Circle – a secret guild formed in the early history of the Kingdom of Galifar. It was a group of magicians that sought out the forbidden mysteries of the Daelkyr and the Dragon Below. The Closed Circle was destroyed in 641 YK by the combined forces of the Esoteric Order of Aureon, The Guild of Starlight and Shadows, and the Church of the Silver Flame.