Environments are important. You could be a crack hack wizard and still suck because of distractions.

The first and foremost important piece of your work environment is your chair. Make sure it's something you can be comfortable in for hours at a time, especially when coding. Get your feet off the floor and onto something. I personally use a high back leather chair and matching footstool. Medically, having your feet dangling or poorly supported for long periods of time is bad for you. Make sure you can lean back in your chair, and you're not working hunched over.

Match your chair to your desk, with regard to height. Find a working position between the two that's comfortable, or work out a way to get your keyboard lower. Ergonomics, while froofy, aren't a joke.

Noise suppression. If you're a coder, get some good noise cancellation going. Background noise reduction cuts down on a lot of distractions. Even if you're not pumping music into it, having your ears covered will quickly become a sign to people that you're busy. Train the mammals to send email instead of pop into your cube. I personally use Sony's noise reduction earbuds, which by shape alone are a functional earplug.

Lighting is important. I've had several cases of janitor combat by disengaging overhead flourescents in favor of a gentle incandescent lamp. Don't work in the dark, though. Hormonally, humans (and other diurnal creatures (this excludes Solaris admins)) are stimulated into various modes by light levels. One argument you'll be presented with should you decide to tamper with overheads is 'Safety Reasons'. Don't let this slide. It's YOUR work environment. Ground level strip lighting is just as effective, and less intrusive. Use indirect lighting where possible.

If you're in a heavy corporate environment, it's entirely plausible that certain management types will immediately single you out as a deviant, so use caution.

Some ammunition:
Oklahoma State Doc on Ergonomics and Environments [okstate.edu]: This is a good common sense doc about computer heavy work environments. You can draft a simple checklist based on the contents to see how your work environs stack up.

This document points out something important: OSHA does NOT have a standing (read: enforcable) ruling or standard for computer operation environments. Your employer can simply tell you to take a hike and get away with it. In some cases, I'd say take this up with HR, or rally your like minded coworkers, but given that most corporate HR teams simply don't give a damn, caveat emptor.

In the event your management doesn't go for it, here's a piece on combatting violence in the office [lhh.com].

In any case, do some homework before embarking on this quest. If nothing else, present it in simple financial terms. Personally controlled light environments tend to be less expensive to maintain than mass overhead lighting. No ladders required, less maintenance impact. Lights turned off when cubes are vacated at beer o' clock serve as pro-active energy management.

Single user monitor lamps, like these from Think Geek [thinkgeek.com] ($29.99 each) work very well. They did their homework [thinkgeek.com] about lighting advantages, as well. This brings cubespace lighting down from the ceiling and into the cube.

The drawback to this, and one of the first things managers (and site security) like to point out, is the reduced light level for the rest of the office. It's a perfectly valid argument, and generally brings lighting wars to a screaming halt. This can be replied to with something simple and inexpensive, like these Mini Lights [espenergy.com], which would sit well on the exterior of any cube wall, illuminating the aisle.

As for general office lighting a few well placed torchiere style lamps (check your lamp types, though. Some suck more power than others) provide excellent indirect lighting.