Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Kickstarter - Kickstarter is the world's largest funding platform for creative projects. A home for film, music, art, theater, games, comics, design, photography, and more.
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.