Worth noting that True Grounds will be limiting its wifi as of Feb. 1 (one hour free with purchase of coffee/food, after that you need to pay). Of course I still <3 them.

The public libraries in general have free wifi; if you don't mind going a bit farther afield, Cambridge/Arlington/Lexington main libraries are just much nicer spaces.

I used to do 1369 in Inman a lot when I lived in Union, and if I still lived in Union I'd be doing Sherman and Bloc 11 a lot, but I don't know the wireless situation at 1369 and Sherman (at Bloc 11 it's the same as the Diesel, so not, alas, free).