WowAce

Drops the least valuable item in your bags to make space.

ElfReloaded

Debuff Monitor: A Powerful & Configurable Raiding Tool

nRaidTracker

Constructs a SimC export string for an item without equipping it

Manages the scanning of the auction house in a reliable an efficient manner.

Combat Alert

Allows for easy congratulating when someone earns an achievement.

Seraphim Raid Tracker

Lists Pots and Herbs you got on all chars and allows you to specify color coding

FuBar_ArenaFu

A 'channeling spell'-tracking addon for Affliction Warlocks. Drain Soul, Drain Life/Harvest Life and Malefic Grasp.

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

Helps to track outgoing mails

Display who crossed the charges on Thaddius

Simple language selection for Data Broker

GearRating

Clean looking square minimap with many options.

PlayerNotes

Display the global cooldown around your cursor. (+ other stuff)