1. Track your tasks and projects in a plain text file, todo.txt. A todo.

  2. Doit.

  3. Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

  4. The professional way to send & share files and folders with anyone

  5. Quickly capture what's on your mind and get a reminder later at the right place or time.

  6. An Agile, Open Source, Free Project Management System

  7. Getting Things Gnome! is an organizer for the GNOME desktop environment.

  8. The simplest way to keep notes. Light, clean, and free. Simplenote is now available for iOS, Android, Mac, and the web.

  9. Taskwarrior is an ambitious project bringing sophisticated capabilities to a simple and elegant...

  10. Flexible project management web application

    open-source

  11. Checkvist is a tool to create and share checklists, plans, and outlines.

  12. Create beautiful rich process documents in a simple to follow checklist format. Fast, free and incredibly simple to use.