At the office I try and keep a tidy space, somewhere healthy between OCD and a rats nest. I can typically clean house in 5 minutes to get the room presentable for clients. But I must say, I do like piles. They remind me of what needs to be done, and eliminating a pile equals accomplishment.
At the console I always need a legal pad within reach. Sharpies, highlighters, pencils are usually strewn about. A work order usually sits atop a stack of Mix & EQ mags. But that's about all the desk space I have in my immediate area. To the right we have a client desk and that's played host to a pile or two in its time. Two guitars and a bass stand in the corner, next to the MIDI keyboard that I set up when the need arises. Guitar pedals line the floor just below the patch bay for when I either a) have a free moment or b) need some inspiration.
I try and keep anything that makes noise up by me. Only quiet items should fall into the client domain, coffee table books, Sudoku and other silent time-occupiers. But if we're done with a mix, and you want to kill some time while I'm making files or whatever, sure, you can play my guitar.
I do like to streamline things. Reaching awkwardly over my keyboard for a fader too many times resulted in a new, apple low-profile keyboard. That ache in my right shoulder went away when I unplugged my mouse and started using keyboard shortcuts. Direct result? I got faster both at editing and mixing.
In an attempt to focus my attention a bit I have started using "Spaces" on my Mac. Pro Tools and only Pro Tools gets space 1. Email, internet, and other eyeball drawing distractions get put away in one space. Productivity apps (calendars, ftp, toast, etc.) get another.
But the number one thing that is key to my workspace is a solid, sound-proof door. Not only because it shuts out the noise (distractions) from the hall. But when it's closed, I have my own experimental performance stage. It's total playtime, and nobody but me is there to judge it. I can make all the mistakes I need to in order to get to the right answer, and when I emerge a genius it's only because no one else heard all the failures. ;) Plus, no one wants to hear you rocking out during your free moment when they aren't as lucky!