This is a page from the Cascading Style Sheets Working Group Blog. Some other places to find information are the “current work” page, the www-style mailing list, the Future of CSS syndicator, and the issue list on Github.
Do you want to know how the CSS WG works? Fantasai has written about:csswg, An Inside View of the CSS Working Group at W3C.
Since the Flexbox workshops seemed to be helpful, fantasai is planning to organize a few Grid Layout spec workshops. There will be one in SF this month; add your availability to the Doodle if you’re interested. NYC and/or Philadelphia next month probably. And if neither of those work, you can get a group together to run one yourself—there are instructions for running a CSS spec workshop that anyone can organize.