Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
MailClark - The Slack bot for external communications