Modkit - Modkit is an open-source programming platform that allows programmers with a variety of backgrounds to share their creations and learn from each other and is allowing programmers to make beautiful software.
Arduino IDE - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware...
MINIBLOQ - miniBloq is an open source graphical programming environment for Multiplo™, Arduino™, physical computing devices and robots.
PlatformIO - Next-generation IDE for IoT
Visual Micro - Arduino IDE for Visual Studio and Atmel Studio
XOD - A visual programming language for microcontrollers. Like code, but better.