WowAce

Changes several of the popup dialogs to not close when hitting the Escape key.

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

Hold a key to temporarily center and magnify the Minimap.

Replacement for default bags.

A fancy LDB reputation display, show faction reputation and reputation change history

Simple and easy to use unit frames.

Library that provides a timestamp that is equal across clients' timezones and system clocks

Auto-assigns raid targets to group member's crowd control abilities

Test whether the player can really dispell a buff or debuff, given its talents.

Tracks buffs/debuffs seen during fights, for post review.

ScrubbingUI

Templar is the ultimate Mage Assistant

OneChoice tries to help you reduce quest reward choices down to, ideally, one choice.

Death analysis tool

Auto Dinger

Provides search functionality to the chatframes

InspectFix

Muffin

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

Calculates a point value of all stats on an item based on relative stat value