WowAce

Adirelle's unit frames, based on haste's oUF.

Mining data for Ackis Recipe List.

CandyBar style cooldown display

Dropdown library for Ace3 options, extensible to other options formats. Works ok.

Keeps track of your current location.

Adds your name to chat messages

ItemPriceTooltip

Provides the /in command for delayed execution.

Raid loot tracking and text generation

Add-on that allows you to setup and quickly switch between different profiles of your action bars

Tracks the HoTs you cast.

Dynamic item DKP calculation

Displays online friends.

Mutt (Macro Update Target Tool) provides slash-commands that can patch the predefined targets in your macros.

Loudmouth

XRS

Checks your gear before bosses and yells at you if you're an idiot

Adds unreal tournament style sounds to PvP encounters.

Shows mana usage as a percentage in a spells tooltip.

Highly-configurable shield / absorb tracker.