Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Mixmax Calendar - The fastest way to schedule meetings with anyone, anywhere
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Bigtent - BigTent is a web-based organization and communication portal for groups.
Calendly - Say goodbye to phone and email tag for finding the perfect meeting time with Calendly. It's 100% free, super easy to use and you'll love our customer service.