WowAce

Chat addon, filtering messages and UI changes

Give whispers an instant messenger feel.

A powerful, comprehensive utilty for displaying graphics and information based on buffs, debuffs, and other triggers.

Show what quests have changed

Tracks rare drops, including companions and mounts

Show item levels in the character frame

Drop the cheapest thing you're carrying

Show a texture on demand

Scan for rare mobs so you can find them and their loot

Point to quest POIs on your minimap

Watch tooltip updates to announce when you find specific objects

Library of data about what items tier tokens can be turned in for

Show the appearance of an item when you mouse over it

Library to check whether an item is equipable / appropriate for a given class

Show vignette icons sooner

Open all your mail

Should I send that recipe to my alt?

The original HandyNotes source for where things are in Battle for Azeroth

Remember locations that city guards direct you to for HandyNotes

The original source for where things are in Pandaria