
Mods that will help mark targets: (I personally just bind keys to the icons)
Displays a circular menu around your cursor with marking symbols while a hotkey is held. The menu disappears when a symbol is selected, and reappears when you select another target.
Raid icon marking that has a radial menu when you double click a mob and a drag and drop bar. Assigned icons will be dimmed.
WoWInterface
Lets you easily classify and mark mobs simply by moving the mouse over them. This allows incredibly fast marking once of trash groups. Although not necessary for the addon to function, you can configure the priority and crowd control methods you wish to use on a per mob basis. You can also customize the marks to use for tank targets and each crowd control method. This allows for consistent marking of targets to tank and crowd control in raid and party situations.
Download, Wowace, Forum
Boss Timer Mods:
Boss alert mod. It consists of many individual "boss modules", mini addons that are designed to trigger alert messages and timer bars for one specific raid boss each. Modules are activated when you target or mouseover a Boss, or if any other BigWigs use in your raid does. In most cases only one module will be running at any given time.
Download, WoWWiki,
Plugins
Boss mods for all raid bosses, Colored raid warnings! Bars can be enlarged when they are about to expire, Some boss mods have very advanced features like the Loatheb healer monitor which allows you to setup a heal rotation and see the cooldowns of all healers, Synchronization system for accurate timers, No dependencies, no embedded libraries, 100% stand-alone, Modular design - all boss mods are plugins and can be exchanged, removed or updated separately, Load on demand - boss mods and the GUI are separate AddOns and they will be loaded when they are needed, e.g. the GUI uses no memory if you don't open it, Efficient code: low memory and CPU usage, Special effects like the screen flash and the screen shake effect to draw your attention on critical events - for example DBM will warn you when Thaddius changes your polarity, Bars can change their color over time and flash before they expire, Many bar designs to choose from, all designes are are customizable: you can change the color, size, icon position etc. Option to create custom timers, so-called "Pizza Timers" for your pizza or whatever you prefer to eat while raiding, Powerful object-oriented API - you can use it to write your own boss mods!
Raid Interface Enhancers:
CT_RaidAssist is your all-around raid mod. It can report hp, mana, buffs, and debuffs of anyone or everyone in your raid. You can set it to notify when someone is debuffed with specified types as well as notify when buffs you can recast fade. It can show 'MT Targets' which allow you to specify MainTanks's which all users in raid can then see. When shown, it will show you the target of the person set as MT. It's a bit similar to the Target's Target function though with this, the tank doesn't even have to be your target.
oRA2 is a lightweight CTRA replacement. It contains everything a raider needs apart from raidframes. It is fully compatible with the messages CTRA sends.
Download, Wowace, oRA3
Cleansing Mods:
This is a cleaning mod. Its job is to help a class that can remove afflictions to do it with ease in every condition (playing solo, in small groups or in big raids).
Download, Wowace, WoWInterface
Threat Meters:
KLHThreatMeter (KTM) is like a damage meter, except it records your threat. By monitoring all the abilities you use and checking your talents, armour set bonuses and buffs, the addon can recreate the threat list of a mob. This makes tank transitions simple, and allows DPS to maximise their damage without pulling aggro.
MyThreat is a simple compact frame containing three simple values: Your threat percentage relative to the current target's threat, Your threat difference relative to the current target's threat, Estimated time to surpass current target's threat assuming constant TPS.
Download, WoWInterface
Omen is a threat meter. Basically, enemies in WoW decide who to attack by deciding who is the most threatening based on the abilities you use. What Omen attempts to do is provide reasonably accurate estimates 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.
Download, Wowace, WoWInterface, Forum
Buff, Elixir, Flask Trackers:
Checks Raid Buffs, Elixirs/Flasks, Pally Buffs & Alerts who breaks Polymorph/Shackle.
Download, Forum
RABuffs makes buffing and raid status monitoring easy by displaying information that you are interested in in a compact window. Each watched aspect is represented with a status bar, capable of displaying three different segments - typically divided into buffed, fading soon and expired buffs.
Checks for raid buffs (including Paladin buffs), food buffs, elixir/flasks plus more.
Download, Forum, Wowace
A tool for raid leaders and members who don't want to use raid frames because they aren't in need of them (melees, caster etc.). It shows 6 different types of bars: alive, dead, life, mana, range, offline, pvp, afk.
Download, Wowace
Respaun Timers:
Provides respawn timers for instance trash.
Download, Wowace
Misc Raid Mods:
Conditioner is a simple raid status frame that shows total raid HP, total healer mana and total DPS mana.
You can easily assign Healer and DPS roles to people by dragging the two icons on the left side of the frame and dropping them on the player you want to assign.
WoWInterface
PvE status frames. Shows marked mobs, you cant click the frames to target though.
Download, Forum
A simple add-on to easily send fight tactics to yourself, your party or your raid. Includes tactics for a number of bosses but not all.
Curse