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.

SocialEngine - Socialengine PHP: Elevating Your Online Community Experience.

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

phpFox - phpFox is a powerful social network platform for niche communities

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

EasySocial - Social Network For Joomla to grow your communities with the least time.