WowAce

Redirect character errors, system messages and information messages.

Automatically turns on the combat log for selected instances

Lightweight Chat Improvements

Static library of wow map data

Bulk mail reception made really easy

Complete tradeskill information.

Provides one or many informational windows with optional interactive widgets.

Marks the locations of Midsummer Fire Festival bonfires on the worldmap and minimap.

Floating Combat Text of awesomeness. Caw. It'll eat your crackers.

Unit frame addon using Ace3.

Timers for Buffs, DOTs, CC effects, etc..

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

Auto repair + shows durability.

Watches your chat, flagging missplled words, and offering correctly spelled suggestions.

Reports on a configurable dashboard or to group chat on consumables, buffs, AFK, mana and many many others but in an intellig...

Drop the cheapest thing you're carrying

Lightweight but powerful auction house interface

Point to quest POIs on your minimap

A replacement tradeskill window

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