WowAce

ItemSync the happy item gatherer and toolkit.

Replacement for default Rune Frame and more.

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

HiveMind

A library for PvP and Battlegrounds

Powerleveling guide framework

ClosetGnome_Switcher

Gives detailed descriptions of particular localities, as zones or instances, and provides optional TomTom integration.

Detox

Pet Theory

FuBar_CheckStoneFu

SysMon plugin for any DataBroker display.

Provide plenty of links

Smooth combat HUD based on ArcHUD2

OneBag is a replacement for the default game bags that combines all the bags into one frame.

FuBar_InnboundFu

Bind spells, items, and macros to keys, without using action buttons

Need Greed window for EPGP lootdistribution.

Suppresses chat messages from damage meters and provides single chat-link damage statistics in a popup.

An auction house AddOn to make the life of each fence easier.