WowAce

Display an informational fighter jet style HUD while flying or riding

ClosetGnome_Mount

Simple display and management of Away / AFK / Busy / DND status via broker or minimap

item2phpBB

Talented_Data

Shows class colors on player nameplates and names

Raid loot system.

Swiss Army knife for instances, including player tracking, ignore buttons, loot tracking, notes, and more.

Announces Mage Spells in chat.

Battleground Timers in a HUD around the Blizzard BG status

EQCompare

Leveling guides for trade skill professions.

opens/closes all bags when at merchant (instead of only the backpack)

HealComm-2.0

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

The One-Key-Mount™ — Simple to use, configured with Rock

Tracks SendAddonMessage Spam

Provides the ability to suppress specific spellcasts like "Deaden" from your casting bars.

Monk Brewmaster/WindWalker Priority and Buff/Debuff Tracking Tool

PriceTag