WowAce

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

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

Chat addon, filtering messages and UI changes

A library for transmitting and receiving latency information of players.

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

Give whispers an instant messenger feel.

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

Makes the default frames moveable via simple drag and drop

Displays additional information for Mythic Keystone dungeons

Replacement for the default UI's StaticPopup dialogs.

Modular casting bar.

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

Library that handles chat output.

The original source for where things are in Pandaria

Postal: Enhanced Mailbox support

Parses ToC and adds About panel to Interface options

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

Show item levels in the character frame

A skinning engine for button-based add-ons.

"Debug" code free since '93!