Sitting here by the window so I can birdwatch probably isn't the best thing for concentration. Might explain why I get so little done.
I keep my notebook close, and refer to it often. I also like to have my favourite radio station steaming via the net, or a CD playing in the background. Depending on what I'm writing, there can often be reference books close by, as well.
Very little - clutter clutters the mind!
I have an iPod ready for when I'm editing. And figures of Darla from Buffy the Vampire Slayer and an Imperial Stormtrooper from Star Wars watching my every move.
Comfort. No TV. Music without words. Lists. Blank paper. Plans and notes in Moleskine notebook. Cats. Water. Art deco lamp. Cushion.
Like most writers, I type at a desk sitting in front of a wall covered with notice boards and post-it notes but they tend not to be a distraction as they're mostly ongoing stuff or completely non-related like wheelie bin collection days (exciting, I know). My desk does get too cluttered though as I'm in the 'do one thing and get distracted by something else' camp so I do need to clear it every now and then. My desk at work is much more organised, although it's bigger. I have a side table at home which I try and keep clear but it's currently cluttered which is bugging me. I've been a PA/secretary since I left school (over half my life ago) so I like to think I'm an organised person.
Music, movies, noise: I need something. Complete silence really freaks me out, and makes me lose focus sometimes.
A comfy chair, music and sometimes photos.
Basically all I need to really get into my writing is my laptop (or a pen and paper) and some music and I can write for hours on end. I've learned over the years to be able to write just about anywhere.
When the room is quiet, I found that I can't get anything out on the paper, or type anything out on the keyboard. I always like to have either the TV on in the background or music playing, while I write...for some reason i focus more on my writing with the noise. as for things, I hate clutter so i like a very clean work space.
It's a bit of a mess, really. I always have paper around to put down my thoughts - as mentioned earlier in answer to another question. I am quite flexible that way and do not require absolute silence or anything like that to concentrate on my writing.
I have an office - a real office, in my home. This has only office equipment, writer related materials and reference books and so forth. It is not a play room where other things can be found, but a professional area where Dave and I work. We each have our own computer now, which is helpful, and share the rest of the equipment. We'll wear headphones or earplugs if other things are going on that are distracting.
Personally, I'll have a tall glass of cold Dr. Pepper, my iTunes playlist to specifically influence the script I'm working on, put my headphones on, and turn it up loud.
I can pretty much write anywhere - I don't need a 'special' work area
No music, no tv. Just silence. And some chocolate.