WowAce

Bulk mail reception made really easy

Estimated range display. Type /rangedisplay for config

Bulk mail sending made really easy

Food/water macro generator

Smooth combat HUD based on ArcHUD2

Chat addon, filtering messages and UI changes

Show what quests have changed

A friendly companion that remembers the chat.

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

Automatically enables or disables combat logging based on location.

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

Loot management tool

A modular, lightweight and screen-estate saving grid of party/raid unit frames

Another HUD addon

Show the transmog appearance of an item when you mouse over it, and shows collection-status in bags, shops, and elsewhere. Works on transmog, mounts, pets, and decor.

Dog-themed unit frames. Woof. Arf. Yip.

EBB adds groups of bars to your screen showing you which (de)buffs currently affect your toon or some other units.

Manages social information with a focus on main-alt associations.

AddOn development framework

Makes the default frames moveable via simple drag and drop