EventsApp - A simple concise app for creating and sharing events.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Event Hunt - Startups and Tech Events Curated By Locals
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.