WowAce

Gnomish math at its best!

ElfReloaded

Communicates with guild members for their positions on the world map

Provides extended aura status settings.

Lets you drag UI frames around

Shows guild and system message of the day only if either one of them has changed since the last login.

Makes those pesky garrison animations go away.

Provides buttons and keybinds for raid flare world markers that never stop working mid-session

Sets you to DND when you fight a boss, and some other crap.

GratuityLib

A helper addon for the achievements "Let It Snow", "Fistful of Love", "Shake Your Bunny-Maker", "Check Your Head", and "Turkey Lurkey"

nRaidTracker

Displays oRA3 main tanks.

FuBar_PetFu

Show an in combat indicator

KC_PlayerFramePlus

Raid target control and instance shortcuts for Broker

Allows for gold tracking across multiple time frames

Assistance for the Ra-den encounter. (Unstable Vita order, ball kill order)

Assist you with faction transfers letting you know which mounts, spells, etc you have and what they will be swapped to.