I believe this to be a complete list of the addons I use and recommend. If I forgot anything, I will update. If you have any recommendation, please comment.
Auctioneer Suite – Scans Auction House for prices so when you auction something, you will know the going price and when bidding, you will know if you are getting a deal or overpaying. I use the “Exit WoW when scan is complete” option and when I want to quit, I just set up a scan and walk away.
http://www.wowinterface.com/downloads/info7879-AuctioneerSuite.html
Titan Panel – Adds an info bar at the top or bottom of your screen so you can quickly see your coords, gold, durability, ammo, XP, FPS, HP/Mana regen, etc.
http://www.wowinterface.com/downloads/info8092-TitanPanel.html
Titan Panel [Itemized Deductions] – An addon to Titan panel which lets you see all grey items in your bags so you can junk the least valuable grey if your bags are full, or if you are at a vendor, sell all your grey items.
http://www.wowinterface.com/downloads/info11422-TitanPanelItemizedDeductions.html
Lightheaded – I use this instead of Questhelper. It pulls all the comments from wowhead.com for each quest. The comments are usually helpful to complete the quest and usually have coords. You can click on the coords if you have TomTom, see next.
http://www.wowinterface.com/downloads/info7017-LightHeaded.html
TomTom – You can either click on the coords from lightheaded or just click on the map to get a crazy taxi arrow on your screen telling you how to get there and the distance. You can also share waypoints to your party if they also have TomTom.
http://www.wowinterface.com/downloads/info7032-TomTom.html
Omen – If you are the tank you need to keep your threat above everyone else and if you are a DPS or healer, you need to keep your threat below the tank. In any event, you need to know your threat on a target if you are in a party. Omen is a threat meter.
http://www.wowinterface.com/downloads/info8459-OmenThreatMeter.html
Recount – Want to know your DPS? Or your heals? Or the DPS and heals of anyone in your party? Recount keeps track of damage and heals and is easily resettable when you join different groups. Not a necessity but something fun to look at while you are riding that griffin.
http://wow.curse.com/downloads/wow-addons/details/recount.aspx
Quest Spam – This is the addon that we use which is whispers in party quest pickup, completion and progression, as well as a DING!!! when you level. It’s actually more beneficial to others in your party than you.
http://wow.curse.com/downloads/wow-addons/details/questspam.aspx
Quartz – It’s a casting bar addon that shows the progress of your casts, enemy casts, and focus, casts. Also shows your latency, buffs and debuffs on your target, and a swing timer.
http://www.wowinterface.com/downloads/info7158-Quartz-ModularCastingBar.html
Atlas – shows maps of instances, bosses, and available loot. More important the more instances you run.
http://www.wowinterface.com/downloads/info3896-Atlas.html
AtlasLoot Enhanced – allows loot tables of bosses to be browsed whenever needed within the game. It can access full item tooltips, show drop rates, allow items to be chat linked and to use the dressing room.
http://www.wowinterface.com/downloads/info5541-AtlasLootEnhanced.html
Fishing Buddy – If you own a fishing pole, download this.
http://www.wowinterface.com/downloads/info4239-FishingBuddy.html
Ackis Recipe List – puts a button on your trade window (blacksmithing, cooking, etc) that lets you see all the recipes in the game for that profession plus who sells it or where it drops.
http://www.wowinterface.com/downloads/info8512-AckisRecipeList.html
Some classes need:
OmniCC
http://www.wowinterface.com/downloads/info4836-OmniCC.html
Healbot Continued
http://www.wowinterface.com/downloads/info6096-HealBotcontinued.html
When you start raiding, you’ll need BigWigs:
http://www.wowinterface.com/downloads/info5086-BigWigsBossmods.html





I forgot a few:
Postal – Instantly get all your mail from the mailbox with one button, Alt-click items to mail them, and it remembers friends and guildies in a contact list.
http://www.wowinterface.com/downloads/info11187-Postal.html
Tank Points – If you are a warrior tank, or probably a paladin tanks these days since they wear the same gear, Tank points lets you evaluate gear – either for effective health or mitigation.
http://www.wowinterface.com/downloads/info6419-TankPoints.html
Item Rack – Lets you see all equipable items per slot plus you can create different sets for different events.
http://www.wowinterface.com/downloads/info4148-ItemRack.html
GoGoMount – OK, I only included this because I think it’s neat and it really serves no important purpose. If you are a mount collector, it picks a random mount everytime you click the macro.
http://www.wowinterface.com/downloads/info8272-GoGoMount.html