WowAce

Library providing multi-column tooltips.

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

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.

Set and manage character notes that are displayed in unit tooltips and /who results.

A fancy LDB reputation display, show faction reputation and reputation change history

Lightweight but powerful auction house interface

Simple and super light-weight tracking of profession links for all your alts.

Collectinator is an addon which will scan your pets and mounts and provide information on how to obtain them.

Item stat breakdown, analysis and comparison

Complete tradeskill information.

StarTip (Tooltips from Outerspace)

Adds various information based on PeriodicTable to item tooltips.

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

Tooltip of awesomeness. Moo. It'll graze your pasture.

Kaliban's Class Loot List Star Display

Dynamic item DKP calculation

Healer gear benchmark

Displays item durability and repair cost.

Shows where the equipment of inspected users or yourself is from.

Shows mana usage as a percentage in a spells tooltip.