WowAce

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

A library that handles the basics of "window" style frames

An addon to assist with organizing healing in a raid set up.

Separate indicator for your HoTs with timer.

Displays classes and specialisation dependent stat priorities provided by icy-veins.com

Cartographer_nnTrainers

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

Allows you to browse your clients database

Allows tradeskill usage by clicking items or reagents.

TGuildFrame

Mutt (Macro Update Target Tool) provides slash-commands that can patch the predefined targets in your macros.

Broken in Midnight. I recommend MidnightFocusInterrupt instead.

Dropdown library for Ace3 options, extensible to other options formats. Works ok.

TouristLib

NRT_EPGP

RicoMiniMap

DeuceCommander

World of Warcraft Classic addon to display current zone information.

Keeps track of current money and all your characters on one realm.

Gathers statistics on certain chance-on-use spells, also known as procs.