WowAce

Shift-clicking on a user name in chat shows a tooltip with their whois information.

Privacy2

Captures chatframe Tradeskill Links for later reference in an easy to read format

Allows communication to be shared across realm through Battle.net.

vChat

TextSpy

Colors friends/bg score board/who list names by class color

Automatically sends guild recruitment ads to the GuildRecruitment channel.

Sets you to DND when you fight a boss, and some other crap.

Shows guild and system message of the day only if either one of them has changed since the last login.

Two-way radio functionality for IC communication

Send Mail to Groups

Bug fix for the Blizzard calendar -- prevents unexpected window closure while editing events

Serialized

Displays current LFG Tool times and warns when ready

A simple broker display that displays in-game and RealID friends in a tooltip.

Enables cooldown notification between players and allows party members access to each-others spell books.

A system config addon to WOW

Check for flask/food buffs

Tattles to your default chat frame who has used their taunt nearby