Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.

Orgzly - Outliner for notes, tasks and to-dos

Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

MemPad - MemPad is a plain text outliner and note taking program with a structured index.

Nuclino - Nuclino works like a collective brain, helping teams bring all their knowledge, docs, and projects together in one place. It's a modern, simple, and blazingly fast way to collaborate.

Workflowy - A better way to organize your mind.