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.

Dropbox - Online Sync and File Sharing

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.

Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.

Filestash - Filestash is a modern client for FTP, SFTP, S3, WebDAV, Minio,...