Here is the addons I use on Ribbed:
Archy - Archeology made easy
ArkInventory - Bag Manager
AtlasLoot - Loot Searcher
Auctionator - Auction UI
Bartender4 - Bar Modifier
Castbars - Custom Castbars for everything (I have targets castbar right where I have the arrow for icehud at on the pic below)
Cooldowns - Puts cooldown timers on all your icons
DrDamage - Puts avg damage on each icon based on buffs/etc
Elkano's Buffbars - List buffs in a text format, allows for custom windows, i have my procs lower so i can see them easier, below that it list any debuffs on me
EPGP - Raid Attendance and Tracking
EPGP Lootmaster - Raid Attendance and Tracking
IceHud - Customizable to keep track of just about everything, keeps track of anything that i need to refresh during an encounter
LootRollMover - moves the loot roll window out of the way
Omen3 - threat meter
oRA3 - tracks raid cooldowns, allows for autoinvites
oUF - works with spartan to clean up the frames
Prat - cleans up chat windows, allows for more options
RatingBuster - allows better mouseover comparasion of equipment
RazerNaga - integrates my mouse better into wow
Recount - combat parser
RobBossMods - in game walkthrus for bosses
ScrollingCombatText - replaces in game combat text, can move it to multiple locations and have it display only specific information
SpartanUI - the gray bar, unit frames, map, etc
Taunt Tattle - reports to me whoever taunts
TauntMaster - keeps track of who has threat on targets, color coded so you know whos tanking what, left click on a name to taunt the mob attacking that person, right click for aoe taunt
TomTomLite - directional arrow
Deadly Boss Mods - keeps track of everything going on during the raid
(click to show spoiler)