WowAce

Postal: Enhanced Mailbox support

Library that handles chat output.

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

Database of item upgrade IDs

Toss those bugs inna sack.

Displays additional information for Mythic Keystone dungeons

Chat addon, filtering messages and UI changes

Library providing multi-column tooltips.

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

Restores access to removed interface options in Legion

Makes the default frames moveable via simple drag and drop

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

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

Tracks rare drops, including companions and mounts

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

An intuitive keybindings library.

Give whispers an instant messenger feel.

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

Replacement for ActionButton_Show/HideOverlayGlow APIs

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