Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Skype for Slack - Move your slack discussions to a group skype call
Membee - Membee is web-based membership management software.
Aircall Now - Make voice calls inside Intercom Messenger 📞💬
Galette - Galette is a membership management web application towards non profit organizations.
Calls on Slack - Make voice calls in Slack