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.
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
Bigtent - BigTent is a web-based organization and communication portal for groups.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Nabble - Nabble is a forum software that are embeddable and fully customizable with scripting language.