The internet is great at distracting, and for me I can't necessarily disconnect because I rely on the internet for certain aspects of what I do. I find that unplugging the laptop and going to a remote location (maybe a Starbucks or something?) is really helpful, leave the power cord behind. You still have the net, but you've got a 3 hour countdown until your laptop dies... suddenly minutes count and there is no time to get lost in rss feeds.
When/If the laptop dies... I can always head back and plug it in, but at least I'd given myself a dedicated block of time on the problem.
Pull the plug on the internet altogether when you catch yourself being distracted. After about 15 minutes once you're into the problem it doesn't matter too much if you reconnect it.
Physically pulling out the network cable from the router (presuming you're at home/in a place where you can) is also a beneficial psychological push to get on with your work.
I do this and have found myself opening Firefox/Outlook/Newsgroup/RSS readers only to find a flat "no connection" page - that immediately scolds me for sidetracking and I get on with what I'm supposed to eb doing again.
Most laptops feature a button to turn off the wireless connection. I find hitting that button has a similar effect, you've just got to restrain yourself from hitting the button again.
My work is writing, so I find it extremely convenient to have internet access as it helps with checking if I've got the meaning correct for words I rarely use in common conversation. It also helps greatly with research, however there comes a time when I have to turn my wireless off and actually use what I've research, etc.
It's OK to expect little payoffs constantly. Split up tasks in small chunks and tick them off as you complete them. Large tasks seem daunting. Small tasks are just that "tasks". Stuff you do without really worrying about it.
Using a TODO lists when you already know roughly what you have to do can help enormously. The mundane act of ticking off a box next to a small task is enough motivation to get started on the next task.
Especially in the morning it can be tempting to "catch up" with all the HN posts, but if you go through your TODO list and see that you have to "fix link on page X" it's really easy to just do it. Only takes a minute. You know what you have to do, and it doesn't "feel" like work. And when you've started the next task automatically follows.
You can even put off simple tasks so you can do them whenever you're not feeling motivated, just to help you get started.
I think that this aspect is actually the unsung hero of TDD.. it provides immediate consistent salient feedback delivered frequently, which is pretty much textbook key to accommodating ADHD.
I try to do things that I enjoy. Something that I would do (or would like to do) even if it didn't have any monetary payoff. If you can find a project that you would do, rather than read the net, and it happens to pay the bills then here is your journey.
This is, of course, quite a bit simplified. In any non-trivial venture there will be a significant number of things that need to be done and that you don't particularly enjoy doing. But if the greater part is fun then it is easier to sometimes buckle down and get through the mundane parts.
I guess it also largely depends on the personality. I, for example, hate having to do something quickly, without fully understanding the area, and moving on. On the other hand, if I have a chance to spend time and get exhaustive knowledge about something then I genuinely enjoy working on it even if on the outset it seemed unattractive (think sales, marketing, writing, etc., vs hacking some interesting piece of software).
I recommend a book by George Leonard called "Mastery: The Keys to Success and Long-Term Fulfillment". It talks about this topic... very fascinating and useful read (also quite short)
