Fhem is a GPL'd perl server for house automation. It is used to automate some common tasks in the household like switching lamps / shutters / heating / etc. and to log events like temperature / humidity / power consumption.
A free (libre), open-source (GNU GPL), content management platform designed for group collaboration. Open Atrium is based on Drupal (running on Apache, with a MySQL database).
Open-source server application packages for deployment as appliances (e.g., virtual machines) or sandboxed local installation on Linux, OS X, or Windows. Smaller application downloads are available to pair with LAMP, LAPP, and Ruby base stacks. Handy for test-driving applications.