WowAce

Should I send that recipe to my alt?

Enables multi-line/unlimited-length pasting of text or commands into WoW

Loot management tool

Sorts the Wardrobe

Death analysis tool

QuestLog

A Simple World of Warcraft Spam Filter!

Additional information about player spells.

Simple right click casting.

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

GDKP gold run ledger

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

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.

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

Angry Assignments

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

An intuitive keybindings library.

Adirelle's bag addon.

XP bar using Ace3.