Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Streaks - The to-do list that helps you form good habits.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Taskful - Deadlines, meet your match.
Slack - A messaging app for teams who see through the Earth!
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.