WowAce

Allows the user to preview and track their progress in the collection of various transmogrification appearance sets

Dynamic mount macro generator

OneBank3 will combine all the bank bags into one frame.

Textures for Stop Motion

A replacement tradeskill window for Classic

An extension to the default WoW Unit Frames.

Simple Spell Alert

Adds various information based on PeriodicTable to item tooltips.

Shows skills in a tooltip and allow them to be used. Also keeps track of Cooldowns.

Keeps account of attendance and loot for raids, parties, bgs, arenas and solo for questing.

Shaman totem bar

Database of item upgrade IDs

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

Prat

Angry Raid Points

Visualises healing.

XRS

The Talent Template Editor

Displays online guild mates.

AutoMagicly clicks though Daily Quests, and Turns them In.