Dropbox - Online Sync and File Sharing
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.
Google Drive - Access and sync your files anywhere
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Nextcloud - With Nextcloud enterprises host their own secure cloud solution for storage, collaboration & communication from any device, anywhere.
Slack - A messaging app for teams who see through the Earth!