WowAce

Show optimal path for artifact leveling

Handles the assignment, coordination, and announcement of many parts of the Lich King encounter in Icecrown Citadel.

Customize the appearance of the chat bubbles.

BananaBar2

BossWhisperer

Automatically invites player from templates.

Displays info about who rolled Need/Greed/Pass on items that are currently rolled for

Omniscience

Saves who searches in a favorites list.

A popup menu containing user-programmable scripts.

A Perl layout with oUF.

A simple addon that warns you if your pet isn't attacking while you're in combat.

cgCrafty

Right-click on minimap blips to open a targeting menu (out of combat).

Auto sizes frame layout depending on group/raid size or predefined zone data

ImprovedTargetFrame

Does a /who search of multiple dungeons.

FuBar_BongosFu

Adds Raid Target Icon status to Grid (Player or Player Target).

GearRating