Yammer - Yammer is a leading enterprise social network used by more than 200,000 companies worldwide, including 85% of the Fortune 500, to get work done smarter and faster. Sign Up Today.
EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.
MS SharePoint - Share, organize, and discover information with Microsoft SharePoint. Learn about SharePoint Online, OneDrive for Business, and Apps for SharePoint
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Communifire - Enterprise Social Collaboration Software
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.