WowAce

Library providing mappings between trade skill recipes, spells and created items

Violation

Antagonist

Co-ordinated targetless Party and Raid wipe recovery. Evolved

Automated smart raid marking to speed up trash clearing in instance runs

Display aura information inside action buttons

Reports in raid chat whenever a raid member "fails." /EnsidiaFails to configure.

Show where the chests are for Withered Army Training

Database of Vendor locations for HandyNotes

Angry Assignments

manipulate the minimap in numerous ways; move, scale, skin.

Raid Frames using the oUF framework.

Queing of /who and SendWho() queries and a much better interface (see docs), with gurantee to be executed & callback.

Database of Diminishing return categories and general data

MorgDKP

A simple slash-command-based addon for querying item information from the Blizzard servers via ItemIDs and SpellIDs.

Keeps track of your current location.

provides enchanters with a decent tool for managing their profession

Set and manage character notes that are displayed in unit tooltips and /who results.

A replacement tradeskill window