WowAce

Armored man and paper doll durability modifier

Advanced Chat Filtering and Spam Blocking Addon

Opens professions and shows their skill level.

Lists and/or reminds people missing flasks or food buffs at every ready check.

Simple and rich Death Knight rune customizations

Debuff Monitor: A Powerful & Configurable Raiding Tool

LD50_abar

This addon helps with daily quests.

A module that lets you find out what today's dailies are without having to visit the quest givers.

ShammySpy

Show an in combat indicator

EnvenomX

Displays bars depending on your professions

Voyeur

Automatically equip 'Chef's Hat' if the Chef enters the kitchen (Cooking TradeSkill).

SurgeonGeneral Listen CLient

Adds aura indicators to unit frames

Reserve raider tracking for EPGP.

Allows for easy congratulating when someone earns an achievement.

GearRating