Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Trustroots - Travellers community for sharing, hosting and getting people together.
ioBroker - flexible and modular application for the IoT and Smarthome
BeWelcome - Open your door to the world!
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Hospitality Club - Free network of people around the world who offer free accommodation, advice and help when they are traveling - hospitality exchange. Free membership.