Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

RemoteTeam - Remoteteam.com helps remote teams become great places to work with the fully-integrated platform to automates payments and HR tasks.

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

Swipes - Plan projects, take action and discuss.

Bigtent - BigTent is a web-based organization and communication portal for groups.

ApproveIt for Slack - Get approvals in minutes, not days. Right from Slack!