The 4 obvious ones you access from Azan:
- Guild of Archery
- Guild of Hunters
- Guild of Indinera
- Higher Guild of Elves
- Guild of Benevolence: In Azan, in the house of the guy who likes books, talk to his daughter on the right and she gives you the map to the guild. Use the map from inventory to travel to the guild ( same with the other guild maps )
- Guild of Inexistence: In SR#80 a man gives you quest #13 ( Ruins of Lyakine ), go to room #81 to find the book, go give it to the man and he gives you the map to the guild.
- Guild of Shadows: You can buy a "Ticket to Hell" from the Forlani innkeeper. At Forlani village, after you get Wendala back, an NPC appears at the top right corner. She trades the Ticket for the guild map.
***Make sure to buy the ticket before you rescue Wendala, otherwise the map lady will not appear.
- Guild of God Slayers: Talk to someone at the Killer Pit ( it was before the level where you find Wendala ). From the starting screen in the Pit, go straight up and fall into the center hole, walk all the way down, on the left side room is a man, just talk to him and he gives you the map (moderator edit: unless you've slain 34+ bosses, in which case Louthros must have ~300 luck in order to get the map).
Fell free to correct me, add more details, post other guilds that you have found or even expand the list by adding the quests of each guild!

EDIT: Ok, edited the post with the correct info.
Moderator EDIT: fixed the info (OP cannot do it themselves)