WowAce

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

Chat addon, filtering messages and UI changes

Give whispers an instant messenger feel.

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

Shared handling of alternate identity data between addons.

A friendly companion that remembers the chat.

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

Lightweight Chat Improvements

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

Redirect character errors, system messages and information messages.

Prat

A blizzard group finder replacement

Configure triggers to send messages to your raid team such as timers, rotations, and health/power based triggers. Raid smarter not harder.

A Simple World of Warcraft Spam Filter!

A Collection of Automations and Interface Tweaks.

Tracks SendAddonMessage Spam

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

Says random things in chat when casting any spell or ability. Type "/ss help" for the user's manual.

A collection of useful (guild management) tools and utilities for smarter than average bears.

Mutes various chat related annoyances while in capital cities and instances.