OP: For noise, really good noise reduction headphones are the key to my sanity in the workplace.
As for internet distraction, I found two things helpful. 1) Eliminate non-essential immediate/push notifications. and convert them these tasks to on demand type tasks. Turn off twitter notifications on the iphone, shut down your IM client, and only check your feeds when you want to, not when they get pushed to you. I find the interruption of the notifications plays hell with my concentration. 2) install rescuetime and track (or even block) your internet sites.
Used under physician supervision he (w/doc) may find a dosage and plan that works for him. YMMV.
Honestly, I tend to use my imagination to concentrate. I mean, really stupid things like imagining that my code is slaying dragons or something, or that I'm actually developing software for an asteroid mining platform. Really, use whatever it takes to make yourself INTERESTED in what you are doing.
Also, avoid Hacker News. ;)