WowAce

Open all your mail

Adds the toon name to the alert that your RealID friend has come online.

Omnibus

A Library for stat conversion, calculation and summarization.

Suppresses chat messages from damage meters and provides single chat-link damage statistics in a popup.

Better quest log and tracker

Keeps track of space left in your bags.

Adds party/raid role icons in useful places

A Simple World of Warcraft Spam Filter!

LDB data source for Tradeskill Cooldowns

Displays the locations of Garrison music scrolls.

Shows Status Bars that you can drag around and group up for your cooldowns

Separate indicator for your HoTs with timer.

Cartographer_Trainers

Allows you to create icons, which can be customized greatly by user's input. CiR is more than just the usual cooldown tracker.

Displays classes and specialisation dependent stat priorities provided by icy-veins.com

Broken in Midnight. I recommend MidnightFocusInterrupt instead.

Quality of Life Tools for Group questing/leveling

A library that handles the basics of "window" style frames

A tool to appraise, estimate, or judge your equipment against the equipment of others.