WowAce

Saves contents of your guild bank and sends/receives updates over the addon channel

Buffalo2

Configuration library

Show coordinates on minimap

Toolset for tanks, providing information on taunts and other valuable information.

Quest helping: fetching items to use, that sort of thing.

Adds aura indicators to unit frames

Displays friend notes in unit tooltips, at logon, and in /who results.

Shows who controls Wintergrasp and the time until the next battle.

MoBuffs

Don't underestimate your little critters!

ItemEnchantApplication

CBRipoff

Adds indicators to the sides of Grid frames.

Uses guild notes to add alts' main names to chat windows and other places

Automagically draw your weapons !

Hunter 'Misdirection' activity and cooldown monitoring for raids/groups. 'Readiness' aware.

PlayerNotes

TradeStop

Announces ooze kill instructions during the Yor'sajh encounter in Dragon Soul. Highly customizable with numerous helpful feat...