WowAce

RoleCall allows you to easily see the talent specs and roles of everyone in your group.

Tracks profession specific cooldowns and items across all your characters

Talismonger-3.0

Generate a macro with random mounts

Powerleveling guide framework

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

Prospecting and Disenchanting Aide

ItemPriceTooltip

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

LilSparky's Workshop mod for Trade Skills

A library to handle rearrangement of blizzard's frames when bars are added to the sides of the screen.

Klappa

DKP system for all guilds in the Banana Republic.

Creates a broker plugin for all your broker launchers

YssGuildShop

Does stuff for sachmo

Smooth combat HUD based on ArcHUD2

Modular and lightweight party/raid frames.

Customizing your buff display

Tracks SendAddonMessage Spam