Omen Threat Meter
Enemies in WoW decide who to attack by deciding who is the most threatening based on the abilities you use. What Omen does is provide accurate values of your group's relative threat level on individual enemies, so that you can see when you're in danger of pulling aggro (or, if you're next on the snack list if your tank bites it). This info is usually only critical in raids, where only tanks can survive aggro, but it's useful for any multi-player situation.
Auctioneer Suite provides you with the tools and data necessary to make those difficult auctioning decisions with ease. From purchasing to posting, the Auctioneer Suite provides time-tested tools to allow you more time to actually play your characters or play the market. As you will soon discover, it is much more than a simple "Auctioning AddOn", the Auctioneer Suite also shows in-depth information for all game items, such as those used in quests or recipes, enchanting, milling, prospecting and more.
Altoholic is an Ace 3 addon written for people who dedicate most of their time to leveling alts, and who want to have as much information as possible in one addon. The main feature of the addon is the search functionality which allows users to search their alts' bags or loot tables in an Auction-House-like frame (see screenshots). All this with multiple-realms/accounts support.
VuhDo is a raid monitor similar to CTRaidAssist or Blizzards built-in raid frames. Basically this is about displaying the health of raid members in form of clearly arranged bars. VuhDo is primarily directed to healing classes, but will make use to almost any other class. Moreover several healing spells or other actions can be asserted to mouse clicks on those bars (Click-Heal).
Trade Skill Master
TradeSkillMaster (abbreviated "TSM") is a modular addon suite designed to help both casual gold makers as well as experienced auction house goblins streamline their gold-making processes including everything from crafting things to buying mats to snatch (dealfinding) lists to creating and canceling auctions. Apart from the main module there are several other modules that are a must have. These include, Accounting, AuctionDB, Auctioning, Crafting, Destroying, Mailing, Shopping, Vendoring and Warehousing!