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.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Membee - Membee is web-based membership management software.
Slack - A messaging app for teams who see through the Earth!
Galette - Galette is a membership management web application towards non profit organizations.