Combat, Casting, and Buffs:
Autobar - Configurable button bar that allows quick use of all items you're carrying in specified categories (i.e. food/water, mana/health pots, food buffs, etc)
BindPad - Allows you to map spells and macros directly to keystrokes without wasting actionbar space.
Clique - Allows you to bind spells/abilities/macros to button presses (supports modifier keys like Shift, Alt)
DoTimer - Bars with timers for player buffs, debuffs, cooldowns, Dot's, active effects (such as Winter's Chill), and HoT's.
DrDamage - Shows information on abilities/spells in the tooltip based on talents/gear (estimated dmg, crit chance, etc).
EventAlert - Adds an icon and timer for procs that can/should be used (ie. Sudden Doom, Nightfall, etc).
GrimReaper - Detailed combat info on what happened to someone.
HitsMode - Reformats the display of the combatlog and allows better filtering.
IceHUD - Heads-up-display that shows player health and mana/rage, as well as target health and mana/rage in side-by-side vertical bars with percentages.
Mik's Scrolling Battle Text - Will display damage/heals/effects that you receive and perform around the HUD.
Castbars - Player and enemy castbar (also displays latency on player castbar for use with stopcasting macros).
ZOMGbuffs - Easy assignment and performing of buffs for you/party/raid. Will also buy reagents based on you what specify.

Class Specific:
Hunter:
Fizzwidget's Feed-o-matic - Allows you to choose criteria for food choice and bind a key to quickly feed your pet.
Fubar_PetinfoFu - Quickly shows a great deal of info about your pet(s).

Informational and Misc:
ACP - Adds an option to the in-game menu for loading/unloading addons specific to that character (supports load-on-demad mods) and also adds a reloadui button.
Align - Provides a grid to help align UI elements.
AMP - Answering machine that notifies you of any missed tells or AH updates while you were AFK.
BindingsReminder - Will display a picture of the keyboard when you enter keybinding mode to show all keys that active keybinds (includes display of modifer key binds on mousevoer).
BonusScanner - Broker addon with lots of info about your character (stats, gems, etc).
BugGrabber & BugSack - Grabs any UI errors and tosses them into a sack for review later.
Fontain - Allows global changes to font sizes and typefaces (default is Calibri v1).
FishermansFriend - Makes the life of a fisherman a little easier (double-click casting, autoloot, etc).
Fizzle - Adds colored border for rarity as well as durability information to gear on character tab.
FluidFrames - Allows dynamic resizing and positioning of any frame (currently only used for Combuctor).
Mendeleev - Displays extensive info about the moused over item in the tooltip (i.e. what it's a component in, such as recipes/patterns).
Message Redirect - Redirects error messages (i.e. "Out of Range") to a chat window or combat log (or disable them altogether).
OverAchiever - Achievement windows enchancements as well as comparison of your progress in tooltips of achievements linked by others in chat.
Prat - Offers extensive configration of chat frames.
RatingBuster - Shows what stats on equipment equate to in the tooltips (i.e. how much % hit/crit comes from the stat, how much dodge the agility equals, etc) as well as a summary of the net gains/losses of the item compared to what you have equipped.
SLDataText - Condensed onscreen info containing server time, FPS, latency, and mod memory usage.
GoGoMount - Automatically mount using the best mount (configurable, and keybound to Shift-~ by default).
Talented - A replacement to the default in-game talent window.
TipTac - Improved tooltips.
XPBarNone - Highly customizable XP/rep bar.
zMobDB - 3D models for the target frame that can be adjusted (please report offcenter models).

PvP mods:
Capping - Timer bars for BG objectives, BG/arena queues, etc.
Gladius - Small unit frames for enemy units in arenas (allows binding of functions or spells such as interupt, set as focus, etc).

DockingStation:
A top bar (much like Titan) with an extensive collection of drop-in modules. Also included is Fubar2Broker to support the addons that we need that still rely on FuBar.

It displays the following info at a glance:
- Money, durability, number of guildies/friends online, a micro menu (i.e. buttons for character sheet, LFG, Help, etc), number of accepted quests, Free/Total bag slots, and quick talent/gear switching.

It also displays the following detailed info if the icon or above info is moused over:
- Your status with all factions, colored by reputation level
- Experience information (i.e. XP/hour, estimated time to level, etc).
- Amount of money spent/earned that session/day/week as well as money available on other characters within the account.
- Guildies/Friends that are online, their level, notes, and location (guild-only).
- Skills list and level, including weapons, tradeskills, etc.

Unit Frames and Actionbars:
ButtonFacade - Supports skinning of both Dominos and Autobar (currently using the Caith texture).
Dominos - Actionbar mod with a generic predefined layout and basic keybinds/paging (the mod supports advanced paging based on stance/form, keybinding, and virtually any button layout).
KGPanels - Used to create the backdrops for the chat/button frames.
OmniCC - Shows the cooldown of a spell/ability on the button.

Pitbull unit frames with the following features:
-Player, Player Target, Target of Target (ToT), Pet, Pet Target, Focus, and Focus Target unit frames with castbar, class coloring, name, incoming estimated heal amount, and buffs/debuffs that you can cast/cure.
- Party frames that also show pet, the target player and pet, castbar for each, class coloring, name, incoming estimated heal amount, and buffs/debuffs that you can cast/cure (also colors the unit frame red if it has agro).

Grid2 unit frames with the following features:
- Raid, Arena and BG layouts with display of health, class coloring, name, incoming estimated heal amount, and debuffs with a priority given to PvE raid debuffs.

Navigation:
Inflight - Flight time to locations displayed in castbar.
Ping Direction - Will show a large red arrow on your screen showing you where and who is pinging the minimap.
Chinchilla - Square, scalable, movable minimap.

Mapster - A map replacement that shows the full content of zones (including unexplored areas). Also allows scaling and alpha settings. Integrates perfectly with the following mods:
- Tomtom - Using "/way zone x,y" you can create a waypoint on your map in any zone (adds an arrow with distance remaining on your screen directing you towards the coordinate). Also allows Ctrl-Rclick to addwaypoints directly to the map.
- HandyNotes - Create customized notes on the world map.
- Gathermate - Will overlay the map with known node information (mostly-complete database included) on various gathering professions (by default will only show locations for gathering professions you have).
- Routes - Allows you to define a route based on herb/ore/etc information for a zone that overlays on the minimap for quick and easy gathering. Integrates with TomTom for easy navigation.

Instances:
BigBrother - Fubar plugin that allows you to quickly query the consumable status of everyone in your party/raid.
DeadlyBossMods - Provides boss-related timers and notifications for 5-man instances.
Omen - Displays party/raid member's threat for your currently selected target (will also parse KTM data that it receives).
Recount - Damage meter mod that tracks more information then you can imagine (capable of creating graphs and side-by-side comparisons).
XLoot - A loot window replacement to the default blizzard frame with more options.

The following raid tools are installed:
- DeadlyBossMods - A boss mod that includes boss-related timers, notifications and a proximity window for certain events (i.e. Gruul's Shatter).
- oRa2 - A lightweight replacement to CTRaid (responds to all CT commands/requests).

Questing:
tomQuest2 - Lightweight quest log replacement with quick view of watched quests/achievements and their objectives.
Questhelper - Uses a pre-populated quest database to calculate the fastest way to complete your current quests. Integrates with TomTom for automatic waypoint creation.
Lightheaded - Adds comments for each quest from Wowhead so they're viewable in-game (database downloaded and installed - does not query Wowhead each time).