WowAce

Gives detailed descriptions of particular localities, as zones or instances, and provides optional TomTom integration.

Gives a score for your kit allowing easy comparison with others, also colour codes kit based on appropriateness for your level.

Makes the Blizzard options frame movable and resizable

Database of FlightMaster locations for HandyNotes

Displays information about the current zone on the World Map

FuBar_ItemDBFu

Considers an item against all the items you have to determine whether or not it is an upgrade

Heal and decurse by clicking on customizable raid/party unit frames

Shows where the equipment of inspected users or yourself is from.

Pins on the World Map for quests you have not completed yet

Tracks SendAddonMessage Spam

A Data Broker display for combat statistics.

Open inventory items with 1 button

NBuffBars

Provides information of tradeskill and crafting materials that are in the banks and bags of your characters.

WF3sec

Quest library for mob location and other information

LilSparky's Workshop mod for Trade Skills

RS_ClassColors

Modifies the inbox into a scrollable inbox, including open all options