This is my current user interface, I am always looking to improve it but this is my current one I try to keep information that is most important near my toon without restricting my awareness, I have found the following to be a good combination.

User interface Details and breakdown can be found below

A: Chinchilla - Map movement/customisation
B: Minimap Button Frame – MBF is cool, it grabs all the icons around your map and puts them into a frame that you can move around, the idea again is to remove the stuff you don’t need to see all the time.
C: oRA2 - A CT_RaidAssist alternative, another requirement for raiding in most guilds. This is the Cooldown frame
D: DotTimer - Very useful tool for tracking dots and hots. Takes a little setup to get it working the way I’ve got it, but I might write a howto in another post
E: Grid - I use grid although HealBot is supposed to be good as well. I added a couple of Grid addons to place corner warnings for stacks etc too and invert the colors! Makes it so much easier to see who needs heals I think (see my config guide).
F: Dominos with ButtonFacade – I use this small dominos bar to highlight my primary spells that have cooldowns, namely; Wild Growth, Nature’s Swiftness, Swiftmend, Innervate, Tranq and Rebirth. It’s used as a reference and I do not use it to click (well may for res’s)
G: Decursive - great for single click (left or right) decursing/cure poison, I use this for dispell intensive fights like Yogg. When I don’t need it gets hidden I know some of you would say “Why do you need a second unit frames?”. I have found that decursive allows me to dispell much quicker than Grid + Macros.
H: Deadly Boss Mods – must have for raiding, timers and notices etc
I: Doom Cooldown Pulse – this is a cool mod that will prompt you as key abilities come off of cool down. This is a great trigger to hit spells like Wild Growth
J: SatrinaBuffFrame (Player Buffs) -  I have SBF split into 2 frames, this frame is used for buffs.
K: Skada - a recount replacement, really cool features, check out my review here: http://www.upyursh.com/2009/09/addon-review-skada-recount-alternative-or-killer.html
L: Quartz (Player Cast Bar) – Cast bar filled with win, I have grown to really appreciate this cast bar addon, it is especially useful for us Aussies who have latency issues, a nice presentation of when you can start casting your next cast makes it really great for those ‘heads down healing’ occasions.
M: SatrinaBuffFrame (Player Debuffs) -  I have SBF split into 2 frames, this frame is used for debuffs, nice and big and relatively central so I dont loose awareness while watching stacks/ticks etc.
N: Quartz (Focus Cast Bar)
O: Quartz (Target Cast Bar)
P: oUF_Upy & oUF - This is my custom built oUF Layout. Consists of (from left to right) Player, Focus, Target of Target, Target.
Q: Prat - Chat customisation, I have prat setup with 2 windows, general chat rooms like 1. General, Raid, Officer etc and a second purely for healing channel. I also use Prat to also announce important messages in our healer channel to the centre of my screen, calls about people being down etc.
R: Dominos with ButtonFacade – Main Toolbar with my commonly used spells.
S: Dominos with ButtonFacade (hidden) – Opacity set to 0 without mouseover and contains secondary spells as well as pet and class bars.
T: Carousel - Is pretty cool, allowed you to build up a number of Brokers and cycle through them. I use this with MacroBroker to manage my Healing Assigns.
U: ChocolateBar - Fubar type addon but rocks more