WowAce

Notifies you of experience gains

NRT_EPGP

Draws some lovely 3D portraits in the standard Blizzard artwork.

FuBar_NetStatsFu

MessageEvent

Shows Chat as Combat Text

Hitman

MobHealth

eePanels2

Client for MagicDKP which handles standby calls and bidding on items.

Allows frames to be dragged around, without permanently changing their position.

Note + rep tracking for players, with guild data sharing.

Adds a button to your character and inspect window that shows a summary of gear enchants and gems.

Simple library that handles multiple levels of logging.

GratuityLib

Adds Friend and Guild options to the context menu of player units.

EyeCandy

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

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

Reverse Engineering will drill down and search your tradeskills for their elements