WowAce

Bulk mail reception made really easy

Makes the default frames moveable via simple drag and drop

Replacement for ActionButton_Show/HideOverlayGlow APIs

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

Create panels for customizing your UI, sucessor to eePanels

Check the quality of wild battle pets

LibItemInfo-1.0

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

Bulk mail sending made really easy

Show what quests have changed

Automatically enables or disables combat logging based on location.

Manages social information with a focus on main-alt associations.

AddOn development framework

oUF element for highlighting debuffs that are dispellable by the player

Compact rune and proc display for Death Knights.

Animated target indicator

Restores access to removed interface options in Legion

A customizable view of friends and guildmates.

Drop the cheapest thing you're carrying

The original source for where things are in Pandaria