WowAce

Detects specific CDs and spellcasts

Displays online guild mates.

FuBar_FarmerFu

This will keep track of how much you have paid per item in your inventory. Only one of (Auctionator, Auctioneer, AuctionLite,...

Tracks vulnerability debuffs on multiple mobs

ItemPriceTooltip

Automates bites during the Blood-Queen Lana'thel encounter in Icecrown Citadel

BiGOpt

Quest library for mob location and other information

A data broker display, that shows one block per plugin.

Tracks SendAddonMessage Spam

HiveMind

Display an informational fighter jet style HUD while flying or riding

Shows your standings with the factions.

Keeps track of durability and pops up a dialog to repair when you go to a vendor who can.

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

pDebuffList

Raid loot tracking and text generation

Tracking and ranking of dps/hps in a guild.

Adds Outfitter set filters to AdiBags.