Arduino IDE - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware...
B4R - Development tool for native Arduino programs.
PlatformIO - Next-generation IDE for IoT
Circuito.io - Instant code and wiring for your project
XOD - A visual programming language for microcontrollers. Like code, but better.
InstaPart - Build circuit boards faster with parts delivered in <24 hrs