Assemblies have not just been used in protest movements such as Occupy and the 15M movements, but also in the governance of regions such as Rojava.
One of the sources behind this emergence are the ideas of Murray Bookchin, whose writings on the subject have been collated in this book:
Book: The Next Revolution: Popular Assemblies and the Promise of Direct Democracy. Murray Bookchin. Verso, 2015.
Here’s the description:
“From Athens to New York, recent mass movements around the world have challenged austerity and authoritarianism with expressions of real democracy. For more than forty years, Murray Bookchin developed these democratic aspirations into a new left politics based on popular assemblies, influencing a wide range of political thinkers and social movements.
With a foreword by the best-selling author of The Dispossessed, Ursula K. Le Guin, The Next Revolution brings together Bookchin’s essays on freedom and direct democracy for the first time, offering a bold political vision that can move us from protest to social transformation.”