PlatformIO - Next-generation IDE for IoT
Arduino IDE - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware...
B4R - Development tool for native Arduino programs.
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Arduino Eclipse plugin - Where Arduino meets Eclipse
UECIDE - Universal Embedded Computing IDE - UECIDE is aiming to be a generic IDE based on the Arduino IDE...