WowAce

Enable/Disable addons for your character in game

Insanity resource tracker for shadow priests.

ComboSounds

Simple, light-weight, LDB-enabled timer that tracks how long you spend in combat

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

Shows the minimum durability of equipped items on the stats frame.

Add-on that shows which battle pets can be farmed this week

Adds a button to the quest completion interface which allows you to auto equips selected quest Item after completion

Shows your standings with the factions.

Omniscience

Displays friend notes in unit tooltips, at logon, and in /who results.

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

Numen

Manager for DKP points. Requires DKP - Bidder as main Graphic User Interface.

Complain about crowd control breaks.

FuBar_TinyTipFu

Saves Auction House search queries.

Quest library for mob location and other information

Hourglass

Shows you which bosses you've killed next to the raid finder frame.