WowAce

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

Chat addon, filtering messages and UI changes

Tracks Raid/Instance/World Boss lockouts for all your characters, daily/weekly quests, currencies, trade cooldowns, and more!

Give whispers an instant messenger feel.

Shared handling of alternate identity data between addons.

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

Redirect character errors, system messages and information messages.

Watches your chat, flagging missplled words, and offering correctly spelled suggestions.

Lightweight Chat Improvements

A friendly companion that remembers the chat.

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

Blocks Chinese Chat

A blizzard group finder replacement

A simple slash-command-based addon for querying item information from the Blizzard servers via ItemIDs and SpellIDs.

Automate Your GDKP Auctions, Bids, & Payouts

A Simple World of Warcraft Spam Filter!

Adds your name to chat messages

Prat

Manages social information with a focus on main-alt associations.

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