WowAce

Create panels for customizing your UI, sucessor to eePanels

Keeps track of HoTs, DoTs, Buffs and Cooldowns. With audio and text alerts to refresh them.

Manufac

Enables multi-line/unlimited-length pasting of text or commands into WoW

Configurable Castbars

OneBag is a replacement for the default game bags that combines all the bags into one frame.

Watches your chat, flagging missplled words, and offering correctly spelled suggestions.

Displays the remaing cooldown of the action you tried to use

Quest History tracker and shows lists of quests in each category

XRS

Database of Diminishing return categories and general data

Redirect character errors, system messages and information messages.

CandyBar style cooldown display

GotWood

Track all threat redirection ability transfers and cooldowns (Misdirection and Tricks of the Trade).

Regain that wasted space!

Auto repair + shows durability.

PT3Browser

Switch macro depending on zones or BigWigs boss modules.

Automated smart raid marking to speed up trash clearing in instance runs