HeySpace - HeySpace is the only free task and simple project management software with communication and collaboration feature.
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.
The New Dropbox - Enterprise software portal for team collaboration
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.
Flow - Stop managing projects from your inbox.
Infinity - Infinity is a fully flexible work management platform where you can organize all your work, your way.