WowAce

Hotkey interface for spells, macros, other clickables.

Bag and item management utilities

Grid module to emphasize units based on some configured conditions.

FuBar_KCIFu

A Latency Data Broker plugin.

NielasAran

Announce which globule to kill during the Yor'sahj the Unsleeping encounter.

Tooltip scanning library.

SeeingRed

TEALib

A data broker plugin showing your longest fight and your current fight time.

Keeps an eye on someone's distance from you, and alerts you if they get too far.

oUF layout looking like ag_Unitframes and Grid.

A simple addon that warns you if your pet isn't attacking while you're in combat.

Library for tracking mouse gestures

Automatically equip 'Chef's Hat' if the Chef enters the kitchen (Cooking TradeSkill).

Pop a chatframe warning about guild battle standard when boss health reaches 30%

LD50_armor

EasyPet

AllYouCanEat shows information about the following statistics: beverages, foods, bandage types, potions, elixirs and flasks.