WowAce

Library handling communcation for Magic* addons

Easily mail friends, guild members, alts and others

QuestAnnouncer

Heads Up Display with Player and Target Info

Cartographer_Treasure

Expo

Database of important locations for HandyNotes

OneCore is the centralized code shared between the OneBag Suite

DogChow

Displays information about the current zone on the World Map for WoW Classic Era

Allows you to browse your clients database

Shared handling of media data (fonts, sounds, textures, ...) between addons.

Arcana-LFG is a broker plugin to show looking for group information, including call to arms

StitchUI

Provides database of quest giving npcs/mobs/objects for display on the World Map/Minimap

Smooth group roll frames

Pet Theory

Raid loot system.

JasonQuest

FuBar_ArenaFu