Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Voice Principles - Guiding principles for voice design, all in one place
ioBroker - flexible and modular application for the IoT and Smarthome
Alexa Skill Kit - Effortless Alexa Skill development with AWS Lambda
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Actions on Google - The open platform for Google Assistant