WowAce

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

Babble-2.2

Some handy events that should exist in the default UI

Queing of /who and SendWho() queries and a much better interface (see docs), with gurantee to be executed & callback.

A library to help with localization of talent trees.

StatLogicLib

Simple library that handles multiple levels of logging.

Library handling communcation for Magic* addons

TabletLib

A library to provide a clean dropdown menu interface.

A library to help with localization of Zones.

Adds predicted lists for spells while the user types

A library to get currencies' related information

Threat-2.0

IncomingHealsLib

Embeddable chat throttling library with traffic shaping and priorities

Scans your Equipment for cumulative item bonuses and sums them up.

Library providing mouse-click support for LibQTip-1.0.

Various libraries based on LCD4Linux, offering users lower-level UI customizations.

Timerbar embeddable library