WowAce

The original source for where things are in Pandaria

HereBeDragons is a data API for the World of Warcraft mapping system

A powerful, comprehensive utilty for displaying graphics and information based on buffs, debuffs, and other triggers.

Simple and Advanced combined - Bartender4 ActionBar AddOn

Creates and manages secure Action Buttons

Replacement for ActionButton_Show/HideOverlayGlow APIs

Displays additional information for Mythic Keystone dungeons

A skinning engine for button-based add-ons.

Custom widgets for AceGUI-3.0 and AceConfigDialog-3.0.

Scan for rare mobs so you can find them and their loot

Show the appearance of an item when you mouse over it

Library to check whether an item is equipable / appropriate for a given class

Library of data about what items tier tokens can be turned in for

Show item levels in the character frame

Show what quests have changed

Automatically leaves the global channels when inside an instance/raid and restores them when exited.

Chat addon, filtering messages and UI changes

Makes the default frames moveable via simple drag and drop

Give whispers an instant messenger feel.

Displays information about the current zone on the World Map, for WoW TBC Classic