WowAce

Library providing multi-column tooltips.

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

Show the appearance of an item when you mouse over it

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

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.

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

Displays item durability and repair cost.

StarTip (Tooltips from Outerspace)

Kaliban's Class Loot List Star Display

Adds various information based on PeriodicTable to item tooltips.

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

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

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

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

Interacts with TinyTip modules, either integrated or standalone, to provide extra centralized functionality. Required for an ...

Shows mana usage as a percentage in a spells tooltip.