Current player guilds are :
(Official)
Raven Trading Company
Orc Bashers
Crimson Shield
The Freelancers
The Revealing Hand
The Grey Circle
The Vakhar
The Arcane Alliance
Unofficial:
Bloody Hand
Farstriders
Of course this is all OOC information. You character would have to ask around to even find information about some of the more secretive guilds.
NPC groups to which players might join via a CDQ:
http://www.layonaraonline.com/forums/forums/forum-view.asp?fid=75