Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
PartyWith - Connecting people who love to party - anytime, anywhere.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
The Simple Postcard - Text a photo to mail it as a postcard
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
LinkedIn Events - A new way of connecting people from LinkedIn