WowAce

See all incoming casts on your target. Also includes resurrection monitor. Uses libhealcomm-3.0 and librescomm-1.0

Automatically and immediately cancels all in-game cinematics and movies

oUF_HolySmurf

Shows who controls Wintergrasp and the time until the next battle.

ElectrofluxTextronator

Shows the spec of people around you in the tooltip.

Scaffold

oUF element for highlighting debuffs that are dispellable by the player

Tracks interrupts

Adds a simple percentage threat status to Grid.

A Latency Data Broker plugin.

NielasAran

For Developers (of Addons which uses LibWho-2.0): show queues and queries in realtime

AuctionSort

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

Hunter 'Misdirection' activity and cooldown monitoring for raids/groups. 'Readiness' aware.

GameLobby

RBM_AbilityWatch

Reports the total threat on a mob at the end of combat.

GoldenRun