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

BuddyPress - WordPress social networking in a box.

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

Elgg - Opensource social network engine

CherryTree - A hierarchical note taking application, featuring rich text and syntax highlighting, storing data in a single xml or sqlite file.

HumHub - HumHub is a free social network software and framework built to give you the tools to make teamwork easy and successful.