WowAce

Arena unit frames

Simple AceGUI3 dropdown item classes for font/statusbar/sound/etc.

Ackis Recipe List is an addon which will scan your trade skills and provide information on how to obtain recipes. It works fo...

Replacement for the default UI's StaticPopup dialogs.

Database of item upgrade IDs

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

Parses ToC and adds About panel to Interface options

The original source for where things are in Pandaria

A skinning engine for button-based add-ons.

Allows you to view all items from all your characters on the same account, when-ever and where-ever you want.

Estimated range display. Type /rangedisplay for config

Another HUD addon

Shows the possible loot from the bosses

In-game theorycraft. Calculates actual damage/healing based on gear, talents and buffs.

Officially the original source of knowledge of where things are in Draenor during Warlords, in HandyNotes

Modular damage meter.

Simple Map Mod

Simple and super light-weight tracking of profession links for all your alts.

Replacement for ActionButton_Show/HideOverlayGlow APIs

An intuitive keybindings library.