Quest Guides by Duffy
This is a great site to utilize if you are a person that likes to make sure you have not missed any quests as you work your way through Tamriel...there are links to pages for every zone. On each zone page, they show all the quests: achievements, main story line, guild quests (fighter, mage and undaunted), and the rest of the quests are segregated by the areas in the zone. There are helpful hints for each quest that will help if you get stuck.
http://dulfy.net/2014/03/30/eso-quests-guide/
TESO Life
This is a database that you can query for quests: by name, by location, by level, and by type.
http://teso.mmorpg-life.com/quests/