Event Finda - Find events near you, and all around the world.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Kibii - Discover exciting things to do!
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Event Hunt - Startups and Tech Events Curated By Locals
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.