Circuito.io - Instant code and wiring for your project
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
B4R - Development tool for native Arduino programs.
ioBroker - flexible and modular application for the IoT and Smarthome
embedXcode - embedXcode is a template for Xcode.
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation