Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Mobilizon - A free and federated tool to get our events off Facebook
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Balloon - A drop box for your Dropbox
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.