I've also found that adding these sorts of limitations to my work environment—no Wifi, for instance—can really boost my productivity.
I download local copies of documentation and APIs for reference and then set up at a coffee shop near me with no Wifi or power outlets. I find it's most useful at the start of a project when I have trouble just getting something down, sort of like staring at a blank page when you have a paper to write in college.
It's also especially good when the place has no WiFi (a rarity these days) and I'm too lazy to tether my phone.