TeamWork.io 
is based on the real-world observation that people plan and manage their work through email, not gantt charts, pert networks, or other rigid project management methodologies.
It doesn't require you to sign in everyday, and it doesn't force a strict planning system on your project.
Instead, TeamWork.io acts as a silent observer as you communicate with your team. It will attempt to determine the status of each task automatically, as your conversation progresses, and keeps reports you can review at any time.
TeamWork.io works with any email address, and there is nothing to download or install.