openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
ioBroker - flexible and modular application for the IoT and Smarthome
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Domoticz - Domoticz is a lightweight Home Automation System
FHEM - FHEM (TM) is a GPL'd perl server for house automation.
Jeedom - Jeedom is a complete home-automation software.