WowAce

Stores a browsable database of spells that mobs cast

FuBar_DuraTek

Heads Up Display with Player and Target Info

CCBreaker

Searches bags/banks of all your characters/guilds.

Assister

Keeps track of your reagents for buffing.

Tracks the Blood Shield for Death Knights.

Role playing AddOn that shows extra information about characters as entered by the player.

Tracks SendAddonMessage Spam

FuBar_AmmoFu

Compact & customizable filtering, monitoring and grouping of buffs and debuffs

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

Simple Spell Alert

Inventory and bank organizer.

PT3Bar

Adds a button to undress the model in the Dressing room.

FuBar_uGuild

Shows skills in a tooltip and allows them to be used.

Easily mail friends, guild members, alts and others