A quick explanation of what's going on in here, since multiple people have asked recently.

1. Bartender 4 - All you'll ever need to manage your bars including custom size, buttons per row, opacity and placement.  The Bartender4 bar that is in the upper left of my screen I use to watch my important cooldowns with CoolDownCount.  It's near grid and my unit frames.
2. ButtonFacade - Most new Ace3-based addons don't skin themselves.  Instead they make a call out to ButtonFacade to handle the "pretty".  I use a ButtonFacade skin called "Adamantite".  There are literally dozens you can choose from and, most importantly, turn off when you're not using them thus resulting in much less memory usage.
3. SimpleMiniMap - Makes it very easy to move and adjust your map.  Add and remove buttons, skin it, etc.
4. Ora2 raid cooldown location.  I look here (usually) to figure out which druid has a rebirth available.
5. This entire black box, the box around my action bars and the slightly transparent bar around my grid are all from eePanels2.
6. PallyPower - This is just one way to configure the look of PallyPower on your screen.  This is why everyone in raid always has their pally buffs, this mod monitors all the buffs for each class that we've been assigned.  Run a pug sometime with 4 pallys that don't use PallyPower and let me know if you get the right buffs ;)
7. BigWigs message alert location.
8. BigWigs boss timer bars.  Bars with longer time left I keep out of my line of sight to the lower right.  Bars that are about to pop, I keep within my line of sight to the upper left.
9. Ora2 main tank windows.  I prefer to see Main Tank, MT's target and MT's target's target.
10. Chat windows modified and improved by Chatter.  I like it better than Prat since it's much lighter and simpler.
11. ClassTimers shows me my buffs so I might act upon them when they pop. 
12. Grid. Duh.
13. When I set a focus, their target shows up here.
14. Focus target shows up here, complete with very visible cast bars and buffs.
15. Quartz casting bar goes here.  It is my opinion that heales should have their cast bar as close to their raid frames as possible.
16. Pitbull player frame.  I have this highly customized to give me just the info I need.  With a custom skin provided by MediaLib :)
17. PitBull target frame.  Also highly customized for the info I need.
18. PitBull target of target.
19. PitBull target of target's target.
20. Fubar - the Bat Man utility belt of WoW. Everyone should have it. It's also on the bottom of the screen.
21. DuraTek - simple durability tracker
22. ReagentFu - watches my reagents
23. AuldLangSyne guild plugin for FuBar.  A great way to see everyone in guild by just mousing over.