Even if your business is primarily online, you are still going to have offline distractions.
The primary disadvantage of working from home is that other people, whether living in the same house, or friends, have difficulty grasping the idea that just because you are at home, it doesn't mean you aren't working. They will think nothing of talking to you, asking you to do favours and otherwise wasting your time in methods they would never do if you were working at an office, shop, factory or other business location. Don't necessarily start ignoring everyone; just be aware how much of your time can be lost this way and stop it when it starts to take up too much time. Saying "Well, I've got to get back to work now" or something similar will help emphasize that you are actually working.
Phone tag is where you ring someone you need to talk to, find they're not available and leave a message, they ring you back and you're not available and so they leave a message, then you phone them again and miss them yet again, and they phone you back...
It may not go on that long, but it's easy to to and fro trying to get hold of someone you need to speak to. If you can't get a hold of them the first time, when you leave a message, tell them when you'll be contactable and how "Hello John, I need to talk to you about XYZ. Sorry I missed you, but I'll be available from 10AM to 11AM on (landline number) and from 2PM to 4PM on (mobile number)."
If you need to make a lot of phone calls in a day, try to group them all together, set aside a time for doing so, and make them all at once. Mid morning can be a good time; people have been in work long enough that they're in the right mindset, they aren't recovering from dinner, and likely aren't yet looking towards home time. Mondays and Fridays can be the worst days of the week; they're either recovering from the weekend or looking forwards to it.
If you miss people and have to leave them a message as above, aim to leave the time you can be contacted as the time you have already set out for making phone calls.
Whilst one touch might be ideal, in some cases it's actually less efficient. Sort out everything with the first touch, grouping similar types of post together, so that you can deal with them all together on the second, and preferably final, touch.
Blogs, whether personal, business or industry specific all take time to read. There is often useful and valuable information on them, but you shouldn't be spending your most productive hours reading them.
One thing that can be done is to buy a tablet computer or internet-capable ebook reader, and read the blogs with it when you aren't properly working.
We get emails every day, and maybe every hour of every day, or even more frequently if you have enough contacts or active email addresses. Many are junk, even more can be spam, but some need responding to. Some are urgent, although urgent can mean "do in the next day or so," but many can be put aside for later.
As with the phone calls above, also try to set aside a specific block of time to deal with your emails.
Forums and Discussion Sites
Forums are useful. They allow networking with people in the same field, the swapping of relevant information, tips and help. Forums are also far too easy to remain on during the day, constantly checking to see what new posts have been made and reading and responding to them. Even places like myLot, which will pay you for your time there, are unlikely to reimburse you enough for the productive time lost. Once again, try to block out a section of time for reading and posting in forums.
Facebook, and other social media sites, whilst now an important part of any business persons', no matter whether they're primarily online or offline, marketing strategy. Posting your status and comments, looking at other people's or playing massively time killing games like Farmville all waste your time.
As well as the specific internet time wasters mentioned above, general surfing of sites of any type can waste hours of time, whether it's watching videos on YouTube or looking at pictures on Lolcats.