NESN is available via ROKU. I assume it is not free but if you want it that bad it is an option to get it directly through their channel streaming app.
Directv\AT&Ttv NOW carries it, I just noticed it was added to my package a couple months ago. The only thing I would say there is that I have had their service for a while now and grandfathered on an older package with a locked in rate, I don't think they are competitively priced per say but the content and service itself is as good as what I had with them via satellite dish.
You can also stream hockey games live and for free here:
http://www.nhlstream.net/
Can even pick which feed you want, home or away. I use it all the time as I follow a different team. 99% of the time the free stream is in HD so it makes little sense to pay for it. I stream it over my laptop and output via HDMI cable into my TV. Works great! I do not know if this may be subject to blackout for local teams.... although I have watched games on it where my team was playing the B's.