Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Pintask - Pintask is the most customizable Kanban board.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
TaskBoard - A Kanban-inspired app for keeping track of things that need to get done.
Bigtent - BigTent is a web-based organization and communication portal for groups.
buckets.co - Feature rich kanban board collaboration platform.