WowAce

Adds filtering based on your known professions.

Aperture

Assist you with faction transfers letting you know which mounts, spells, etc you have and what they will be swapped to.

Simple oRA3 Maintank Target Frames, based on oUF

Saves Auction House search queries.

Reputation Statistics - Gained, Needed, Rep/Hr, Session Time, etc.

A data broker plugin showing your longest fight and your current fight time.

BangItHarder

Checklist and notes addon.

Notifies the raid when someone is Dazed.

Records mail when visiting the mailbox to make keeping track of mail and expiration dates easy.

XML import library

ChatAssist2

Keeps a list of all items you want and shows how much you need.

LDB display of the players current damage percent modifier

Reminds you to Life Tap and Dark Pact

LDB data source for reputation monitoring.

Add-on that shows in a unit tooltip window a number of killed mobs of the same kind

A menu with useful searches for Inventorian

Customize the PlayerPowerBarAlt display