Quest Completist
Enables you to see what quests you have completed, and what ones you have left to do.
Download for
-
Wrath of the Lich King -
Cataclysm
-
Mists of Pandaria
Wrath of the Lich King 
Cataclysm 
Mists of Pandaria Addon Details
Expansion
Wrath of the Lich King Categories
Developers
Having issues?
Enables you to see what quests you have completed, and what ones you still have to do. Supports server query, allowing you to query the blizzard server for all quests you have completed in the past.
In-Game Commands:
/qc
/questc
Download Quest Completist
More addons for Wrath of the Lich King
Discover other addons that might interest you
BindPad
Keybinding UI for Items, Spells and Macros.
Modern Mouse Over
Macro generator for perfect mouseover casting. Automatically adds macro to hotbar. (For 3.3.5 pservers)
TBag-Shefki
The last bag addon you'll ever need. Autosorting, viewable anywhere, easy to use yet amazingly…
SexyMap
Spice up ye olde minimap with some sexytime options.
Magnify
World of Warcraft WotLK (3.3.5a) add-on that enables world map zoom.
Arcanum
Arcanum is an addon that helps mages with managing their buffs, portals and more.
Atlas Arena
An Atlas Plugin that displays arena maps.
Quest-o-matic
Auto accepting and turning in quests