WowAce

In-game EPGP guild helper, supports standby, main/alt shared pools, minEP, offpecGP. Fixed price list with progress multiplier.

Blocks Chinese Chat

DeclineDuel

Group interrupt cooldown tracking.

Shared handling of media data (fonts, sounds, textures, ...) between addons.

Death reports

DogChow

Provides information of tradeskill and crafting materials that are in the banks and bags of your characters.

Scans your Equipment for cumulative item bonuses and sums them up.

Sanity2

Tell you where all the daily elite pets are

Broker plugin to display player orientation

Displays an alert whenever you loot an item for the first time.

Allows you to browse your clients database

Hemlock

Test whether the player can really dispell a buff or debuff, given its talents.

LDB data source for herb, ore and skinning node data

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

Complain about crowd control breaks.

Tankalyze