WowAce

Unit Frames of awesomeness. Woof. It'll bite your face off.

Database of Trainer locations for HandyNotes

Shows ZoneInfo on the World Map in a perfectly cromulent fashion.

Threat reactive nameplates for TidyPlates.

Aloft

Display front-end for LibGuildPositions-1.0 using HandyNotes

Try on different gear and see their total stats and their differences. In short, an ingame CT-Profiles-like addon.

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

Kaliban's Class Loot List Star Display

Library providing mappings between trade skill recipes, spells and created items

View bank, inventory, mail, equipped and guild bank contents from any character anywhere!

Adds various hearthing items to AdiBags virtual groups

Database sharing module for GatherMate2

Track time played, rested XP and money for all characters

Compact rune and proc display for Death Knights.

Queing of /who and SendWho() queries and a much better interface (see docs), with gurantee to be executed & callback.

The Talent Template Editor

Displays the remaing cooldown of the action you tried to use

Open all your mail

Configure triggers to send messages to your raid team such as timers, rotations, and health/power based triggers. Raid smarter not harder.