PlatformIO - Next-generation IDE for IoT
Arduino IDE - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware...
Arduino Eclipse plugin - Where Arduino meets Eclipse
XOD - A visual programming language for microcontrollers. Like code, but better.
embedXcode - embedXcode is a template for Xcode.
MINIBLOQ - miniBloq is an open source graphical programming environment for Multiplo™, Arduino™, physical computing devices and robots.