WowAce

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

Afflictions display and cleaning for solo, group and raid with advanced filtering and priority system.

Library providing multi-column tooltips.

Chat addon, filtering messages and UI changes

Makes the default frames moveable via simple drag and drop

Library that handles chat output.

Collects Herbs, Mines, Gas Clouds, Archaeology, Treasure and Fishing locations and adds them to the worldmap and minimap

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

The original source for where things are in Pandaria

Restores access to removed interface options in Legion

Replacement for the default UI's StaticPopup dialogs.

Show item levels in the character frame

Give whispers an instant messenger feel.

A modular, lightweight and screen-estate saving grid of party/raid unit frames

Officially the original source for where things are in the Broken Isles, in HandyNotes

Parses ToC and adds About panel to Interface options

Displays additional information for Mythic Keystone dungeons

Collects Herbs, Mines, Gas Clouds, Archaeology, Treasure and Fishing locations and adds them to the worldmap and minimap

The original HandyNotes source for where things are in Battle for Azeroth

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