I find Facebook the most distracting. I was distraught when I found out I could check it from my phone. Damn.
But working to deadlines seems to work best for me. Usually I hate deadlines, but as I set them myself it doesn't matter so much if I'm off by a couple of weeks. Hell, some writing's better than none, right?
Other than Facebook and masturbation, I have no excuses. 
I've deliberately avoided going on to facebook because I reckon that would be that as far as writing is concerned. I only seem to be able to write anything decent after about 10 at night. It's been the same since my student days [which were a long time ago]. So I can take a whole day with the intention of writing something of pure genius and only start then. I think I'm part owl! And I've never seen anything decent written by an owl. Correct me if I'm wrong.
The Who wrote some pretty good songs.
That's an 'owler!