WowAce

A fully featured library tracking all ongoing absorb effects

Records mail when visiting the mailbox to make keeping track of mail and expiration dates easy.

NabuFiveSec

Color manipulation library.

MonkeyPirate

Displays info about who rolled Need/Greed/Pass on items that are currently rolled for

On login, displays changes to your guild since the last time you logged in.

Scans your Equipment for cumulative item bonuses and sums them up.

Simple, nice-looking power bar addon for all classes.

Assistance to the dance during Dread Spray

Don't underestimate your little critters!

Fires events whenever a raid member "fails".

FuBar_FuXPFu

ShadowGreenLight helps you decide if recasting SWP/Corruption is worthwhile

FelwoodFarmer

Automatically switches Profiles of addons when changing spec

Adds Name and Buyout Price sort columns to the auction house.

Displays an animated bar with next enemy swings

Allows for gold tracking across multiple time frames

Simple loot specialisation display with selection in tooltip.