WowAce

Simple display and management of Away / AFK / Busy / DND status via broker or minimap

Buffalo

A fork of BananaDKP.

AceBuffGroups

Loudmouth

Monitors for friendly deaths and announces them as in Myth: The Fallen Lords

A customizable view of friends and guildmates.

FuBar_MicroMenuFu

Library handling communcation for Magic* addons

RBM

Tracks the precise arrival & departure schedules of boats and Zeppelins around Azeroth and displays them on the Mini-Map and ...

AspectsBar

Watch tooltip updates to announce when you find specific objects

A library to help with localization of talent trees.

A Data Broker display for combat statistics.

AltClick an item in your bag to add it a mail, auction, or trade frame, and alt-click to buy a stack if reagents.

FuBar_ChatLockFu

A simplistic clock.

Displays the time remaining before your (temporary) pet is dismissed.

Gives a score for your kit allowing easy comparison with others, also colour codes kit based on appropriateness for your level.