Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
ClickMeeting - Collaborate with partners and clients using ClickMeeting professional web conferencing software. Try it now, FREE!
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Zoho Cliq - Team chat that's built for work
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
GoToWebinar - Webinar & Online Conference | GoToWebinar