WowAce

Gathers statistics on certain chance-on-use spells, also known as procs.

CandyBar style cooldown display

Provides quick access to information on your group and their equipment, enchant and gem choices.

TabletLib

Automatically leaves the global channels when inside an instance/raid and restores them when exited.

Mutt (Macro Update Target Tool) provides slash-commands that can patch the predefined targets in your macros.

Tracks vulnerability debuffs on multiple mobs

Add-on that allows you to setup and quickly switch between different profiles of your action bars

Necronomicon2

A library to provide a clean dropdown menu interface.

FuBar_HonorFu

Reorients the camera to be behind the character after a charge.

Keeps track of space left in your bags.

KillingSpree

Adds a button to undress the model in the Dressing room.

Switch macro depending on zones or BigWigs boss modules.

RootsBidder

Keeps track of your current location.

Co-ordinated targetless Party and Raid wipe recovery. Evolved

A library to help with localization of Zones.