WowAce

GDKP gold run ledger

Keeps track of current money and all your characters on one realm.

Officially the original source for where things are in the Broken Isles, in HandyNotes

Set and manage character notes that are displayed in unit tooltips and /who results.

Save and send chat messages to many channels. Allows quick item and profession linking within your messages.

Adds unreal tournament style sounds to PvP encounters.

Entertaining kill-shot notification.

EBB adds groups of bars to your screen showing you which (de)buffs currently affect your toon or some other units.

Display Cooldown Count of Spell Icon and Item

LibItemInfo-1.0

Automatically enables or disables combat logging based on location.

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

Show what quests have changed

Show a texture on demand

Angry Assignments

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

An intuitive keybindings library.

Adirelle's bag addon.

One large inventory.

The original source for where things are in Pandaria