WowAce

Used to visualize and change values of variables/variable-trees in game

EasyTrack

Cryolysis

Enhances the StackSplitFrame with numbered Buttons, a '1-Click Mode' and a 'Auto Split Mode'.

A PitBull4 module which shows an arrow that points to raid members

Dailies Quest Tracker

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

Tells you which blob to kill at the Yor'sahj encounter in Dragon Soul.

Adds Buff/Debuff icons to the grid frame.

Create reagents easily

Stable

Cartographer_Herbalism

Automatically invites player from templates.

Bidder for DKP points. Usable as standalone bidder, or with DKP - Manager to manage points.

ezIcons

Needja Tracker

GridLayoutPlus

AltClick an item in your bag to add it a mail, auction, or trade frame, and alt-click to buy a stack if reagents.

Waitlist addon with EPGP Mass Award hooking.

Simple and rich Death Knight rune customizations