WowAce

Crowd-control monitor

Speeds up triggering actions such as items or spells by triggering them on key/mouse down rather than release

Library to help with querying unit talents.

Gives a score for your kit allowing easy comparison with others, also colour codes kit based on appropriateness for your level.

GridAlert

Klappa

VitalWatch

A raid buff tracker

VisualThemes

Makes your item stats shine!

Keeps track of gold and cash flow across multiple characters

Ignore more than 49 people, autoshared between your alts

Adds item values to chat messages.

Library to provide non-explicit cooldown tracking and callbacks.

PoisonMenu

Keeps track of honor, PvP statistics, BG Marks, and Arena points.

Library to aid in the classification of Mounts

ItemEnchantApplication

Makes grid QuickHealth aware

LibDataBroker plugin showing some random XP related data