Communifire - Enterprise Social Collaboration Software
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
DigitalChalk - Online Training Software and Learning Management System (LMS)
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
Workplace by Facebook - Connect everyone in your company and turn ideas into action.
Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.