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

ScribeHow - Create step-by-step user guides, with a simple click

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

iorad - Tired of explaining with screenshots? Instant Interactive Tutorials with iorad

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

Archbee.io - Archbee is a developer-focused product docs tool for your team. Build beautiful product documentation sites or internal wikis/knowledge bases to get your team and product knowledge in one place.