One t-shirt idea I've toyed with says "I suffer from A.D." Like a kitten stuck in an office with a kaleidoscopic, jingling ball of crumpled paper, my attention darts from subject to subject, and hence from task to marginally related task with horrible ease. I've learned a few tricks here and there to keep distractions at bay.

1. If you must have some sort of entertainment, use Imeem music playlists or AOL Radio. Add onto your playlists at the end of the day as a reward for completed work and so you don't start closing open windows to constantly play one or two favorites. One of the worst wastes of my time is trying to keep the background music or sound running, to put me into a productive mood. Whether it's finding a YouTube music, comedy, or a long documentary, the minutes I spend at the end of each play become destructive. While it is possible to make a YouTube playlist as well, wading the spam keywords can take forever, and I've found that Imeem is a great tool for getting a solid amount of background music together. If you do use a playlist, move the songs you play most to the top, because listening to that one great song at the end will keep you double-clicking it like a monkey pressing a bar in that infamous narcotics experiment. As for AOL radio, it runs largely ad-free and the music quality won't have you changing it every few minutes.
2. Don't use an integrated web portal that offers 5% email, 5% IM, and 90% ADHD-inducing widgets and gadgets. Swat at your email if you've found you've got it open. Don't get addicted to the illusion that you're in complete control of your work day simply because you're attuned to the click or chime that shows you have another message from someone. Chances are it's spam or something personal anyway. If you can, create a work account none of your friends or co-workers know about, and use it exclusively for business. If you slip and subscribe to an email subscription while on that account, change it to your goof-around email address immediately.
3. Keep only two windows maximum open and make sure they're both business related. Close out everything else. If you're finding that you're reading news stories featured beneath your email, or opening your favorite video to calm your nerves, catch yourself.
4. Practice building your tunnel vision. Many websites you have to work with might have supporting ads and apps and tantalizing stories, but life will go on without knowing which actress has suddenly gotten shamefully flabby, or playing that cool game. Realize how much time you lose with every distracted click, and how you're paying a third party a few pennies and sacrificing your own, far more valuable time, and your employer's daily goals.
5. Disable your Internet connection if you don't need it. Tear yourself out of the grid if you can. Go to your network connections and turn the damned thing off altogether if you're working on a report or collation or some other kind of project that doesn't need you checking every fact. Get used to the less-interrupted way of working without online distractions. Combine it with a turned-off phone if you like. Use CDs instead of music lists, and go 1990's if you have to, listening to store-bought CDs instead of taking 15 minutes to burn your favorite mixes. Tell your boss if you have to that you don't need to anxiously await everyone's information 24/7.
6. Eat well before you start work. If you're running on junk or an empty stomach, you may be bouncing off the walls distracted. Same goes for bathroom breaks. If you're going to get promoted for having an iron bladder, save yourself the misery and quit. And if you're suffering by chaining yourself to your desk simply because you think physical presence means productivity, give yourself those few magic moments instead and get back to work right after. Excuse me for a moment.
7. Visualize your day in terms of dollars and cents. What value are you creating for your workplace? What are you doing that a frustrated boss can't someday outsource to India, China or Russia, or even another in-house employee for $3-$15 an hour? Are you making enough for your employer to be able to pay you and run his/her/their business? If you're your own boss, how much does losing track of the day cost you, both for the short and long term? Think about how a full day's work could be compounding interest ten or twenty years down the road, assuming you earned it. Did you, and if not, why?
8. Play only when you get out of work. Get your fun off the clock, but try to be in a working frame of mind about an hour before the job begins. If it means getting more sleep or cutting out extra things, it will still save you time at the end of your work day if you come in fully charged and less diverted by mental or physical fatigue.
9. Avoid easily distracted co-workers when you can until you get out of work. Lost focus is contagious.
10. Be up front with yourself and your boss if you know there are better, less frustrating ways to do a process. If your boss has no other explanation NOT to act on your ideas, aside from stubbornness, you can take the initiative yourself, plod along at the best rate you can, or find a better job. My old boss had a 1997 digital camera and it stank. I dragged my cup across the bars day after day until they finally relented and bought a new camera (then I quit anyway because they wouldn't use Windows Messenger :D).