WowAce

Fires events whenever a raid member "fails."

Shows Status Bars that you can drag around and group up for your cooldowns

Necronomicon2

Toggles WoW to the forground on events.

A library to provide information about zones and instances.

Compact rune and proc display for Death Knights.

Cartographer_Treasure

Provides quick access to information on your group and their equipment, enchant and gem choices.

Questing minion

Keeps track of your top hits, heals, criticals, etc.

Reduces interface tedium by doing the little things for you.

Inspects all members of raid and saves in database, as well as lists people's dkp values

Threat reactive nameplates for TidyPlates.

Displays the locations of Garrison music scrolls.

A sexy logarithmic cooldown bar

Show what quests have changed

Need Greed window for EPGP lootdistribution.

A simple interface for unitframe click casting.

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

Tracks the current Fear Ward's in the raid or party.