Honeycommb - Social networking solution for businesses of all sizes

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Plek - Community & collaboration platform

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.