WowAce

I've invented a device that tells you when reactive abilities are available!

Echos quest objective completion to your party

KeyBoundExtra-1.0

coolDown

Improved Guild Control Panel

A UI for searching the guild roster.

A library to help with localization of Archaeology artifacts

Shows what stat was reforged in item tooltips.

Experiments in Mana/Regen Tracking

Shows the duration of the most recent (or current) combat

Tattles to your default chat frame who has used their taunt nearby

Adds tooltip for debuffs (and other things? you found out: no).

Provides data about all artifacts in the player's possession.

Printing unknown AddonPrefixes to your chat

Save and send chat messages to many channels. Allows quick item and profession linking within your messages.

RuinBossTactics

With Mists of Pandaria Blizzard publish all characters from an account unless you disable that 'feature'. This addon warns you.

BalerocHealers

FuBar2

A Library for hooking tooltips.