Dropbox - Online Sync and File Sharing
Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
Google Drive - Access and sync your files anywhere
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.
SpiderOak - SpiderOak makes it possible for you to privately store, sync, share & access your data from everywhere.
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.