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.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
MS SharePoint - Share, organize, and discover information with Microsoft SharePoint. Learn about SharePoint Online, OneDrive for Business, and Apps for SharePoint
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
Communifire - Enterprise Social Collaboration Software
Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.