WowAce

Automatically equip 'Chef's Hat' if the Chef enters the kitchen (Cooking TradeSkill).

Plays amusing sounds whenever you skin a mob

Keeps track of gold and cash flow across multiple characters

Checklist and notes addon.

Assist you with faction transfers letting you know which mounts, spells, etc you have and what they will be swapped to.

Fudge

Good looking, smoothy and helpful nameplates

Adds aura indicators to unit frames

ElfReloaded

A boss encounter engine used by other add-ons

Fancy up the ExtraActionButton frame

Display an arrow that points to a raid/party member anchored to raid frames

Libary for cleanly inspecting other players

Library to provide non-explicit cooldown tracking and callbacks.

FuBar_PetFu

Keeps tracks of /rolls.

Target assistance by automatic rewriting of macros

PricePer

FuBar_AssistFu

GearRating