No screenies available at the time.
Bartender (whatever version, I use 3 although 4 is out I think. My preferred actionbar mod)
X-Perl (Unitframes addon, replaces Character, Pet, Target and Party. I disabled Raid and Raid Pet function)
Grid (My preferred Raid UI. Small and simple, yet provides alot of info. Clean screen with that)
CT_Ra (for the raidleaders, they seem to like the info)
DBM (Well, DBM is kind of a must for raiding. That or a couple of other similar mods)
Omen2 (Threatmeter. Best I know of)
Recount (Damage Meter, best I know of)
Quartz (best castbar I know of, universally)
Natur Enemy Castbar (more info than Quartz when you deal with a fuckton of mobs/players)
ZHunter (Saves much needed barspace for things like Aspects and such)
Simple Minimap (Helps with placement and shape)
eePanels (for making things consistent instead of just randomly placed addons)
ArcHud (For gathering player, pet, target and target's target information around your character. Good for those of us who don't like spending time looking for information)
FuBar (Just a plugin gatherer, also shows info about more mundane stuff like latency, gold, repairbills and stuff like that. )
CT-mod (Use some of the functions there, chatwindow arrow remover, mousewheel chat scroll, mailbox functions and map items.)
Gatherer (Saves info about where various resource nodes are located)
Itemrack (To quickly switch between PvP, Raid and City gear. Also useful for my Druid and Warrior (Tanking/DPS/Healing gear takes a while to change without it ))
This is what I can remember right now. Anything else is probably exclusive to other classes, like Totemtimers and Necrosis.
I'll see if I can't find an UI pic when I get home to my own computer.