WowAce

Shows a countdown bar for the duration of auras (e.g. HoTs, DoTs)

Continuation of Shadowed Unit Frames

Shows a money overview for your current realm in the tooltip on the money in your bags

Provides the the health and target of by an unit targeted mob (meant to be used for tanks).

Tracks and announces interrupts (eg. Hit/Miss/Immune) and is also able to track and report "wasted" interrupts (those which d...

Percent

DaPortrait

Dual-box Quest Automation

FuBar_TraxieFu

FelwoodFarmer

Draws 3D portraits for main units that can be moved or resized at will.

RaidGroupNumber

Pop a chatframe warning about guild battle standard when boss health reaches 30%

A collection management library similar to .NET's System.Linq

Improved Guild Control Panel

A library to provide coloring tools.

BalerocHealers

clcInfo module for all Warlock classes

Grid module to emphasize units based on some configured conditions.

Ranged stats Data Broker plugin.