Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Balloon - A drop box for your Dropbox
Bigtent - BigTent is a web-based organization and communication portal for groups.