As DK's we have more than a few cool downs to manage. The best way I've seen to deal with it is classtimer for buffs/debuffs and magicrunes for our actual rune system. Would be interested to see how everyone else is managing with addons and layout. What I am most interested in sparking discussion about here is the different layout of UI's we use as DK's. e.g. How best to organize the information. Please do not just post a link to your UI and a list of addons. Actually explain bit about why you've laid out the information as you have.
About the UI:
I organize my UI this way in order to give myself some semblance of sanity. Default wow UI has frames and information around all the edges of your screen. Couple this with raiding addons like Deadly Boss Mods or Omen and you have to look at 60-70% of your screen all the time, rather than focusing on what is happening situationally while you play. I've tried to keep my UI organized in a vertical column displaying as much information as I can in the mot organized fashion. This way the rest of my screen and attention can be focused on the actual goings on in game.
From my blog:
Spent some time adapting my UI for my death knight. Same basic principles of the regular UI with some twists. Abilities followed by pet bar and player bar. Omen is a bit shorter as I made room for MagicRunes. Magic Runes is a great Death Knight addon that shows your runes and rune cooldowns in a bar format. Completely customizable and skinnable.
Following the rune cooldowns are the target of target and target frames. Immediately below that is the addon ClassTimer. I absolutely love this addon even though I couldn't quite get it to do what I wanted. The original goal was to have the buffs I can cast on myself listed in a single column immediately followed by the debuffs I can cast. The idea being that the list would grow down. Since I couldn't get the addon to do this I split the buffs and debuffs into two columns. The reason being able to see this is so important is because your damage is heavily dependent on your buffs and debuffs as a death knight, especially as unholy.
Rest of my UI is the same but I've made this UI available for download here.