I know that list questions are generally discouraged across the Stack Exchange network; however some communities allow them, e.g. Math... so I guess it's not completely out of the question, and its up to us as a community to decide; maybe the Community Managers have an opinion about whether it's too early to define such scope of the site, however.
Personally, I don't think this sort of post is for us; this is a Q/A board to answer specific questions, not a reference site for everything networking.
With this particular post, it's hard to draw the line IMO; what about geographical communities? Who decides when a community is large, helpful enough (to who?) to be added to the list?
Furthermore, these posts very quickly end up being a big, unwieldy list, generally without any sorting or organisation, and very quickly becomes unusable (can you tell I'm not a fan? :P).
As for how to do this; you can post CW answers right from the off, but to make a question CW, you have to flag it for moderator attention and specifically ask a moderator to CW it for you. Answers to a CW question are automatically CW'd upon submission.