Cost: Free for the basic version; $15/month/user for the premium version.
Available on iOS too? Yes
This mobile collaboration tool from Salesforce.com “makes business processes social.” Users can share and collaborate on files, while also having the ability to comment on files, track versions and receive alerts the minute anything changes. Chatter feeds allow you to monitor sales deals, changes to customer information and project updates. Users can also create team groups, view colleague profiles and monitor both projects and work groups.