WowAce

Library that handles chat output.

Keeps track of group members and keeps an up-to-date cache of their specialization and talents.

Postal: Enhanced Mailbox support

Database of item upgrade IDs

Toss those bugs inna sack.

Library providing multi-column tooltips.

Displays additional information for Mythic Keystone dungeons

Chat addon, filtering messages and UI changes

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.

Restores access to removed interface options in Legion

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

Makes the default frames moveable via simple drag and drop

Tracks rare drops, including companions and mounts

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

Give whispers an instant messenger feel.

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

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

An intuitive keybindings library.

The original source for where things are in Pandaria