Also try Crackbook [1] for Chrome which delays pages instead of banning them. Works much better for me that Stayfocusd, which I just disable after a while. (Disclaimer: I am the author.)
Brilliant. Blocking the site makes the brain want to got around it, as others say. Delaying the site attacks the addictiveness directly, slowly weaning you off the feedback loop. Nice.
It drive my work time successfully now that I work as a freelancer (and I was having your same issues).
[1] http://tomatoes.heroku.com