Facebook Groups - This app gives you a dedicated space for you and your groups
Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Mobilize - Mobilize is a scalable messaging app built for large groups.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Telegram Desktop - Fast and secure desktop messaging app, now updated
Dropbox Paper Mobile - Organize your team’s knowledge in a single place