Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.