Facebook Local - Discover places to go and events happening near you
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Party Bot - A bot that helps find the best parties happening near you.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
LinkedIn Events - A new way of connecting people from LinkedIn
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.