Arduino IDE - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware...
myOpenLab - MyOpenLab is a platform for finished elements (program components) that can be linked together.
embedXcode - embedXcode is a template for Xcode.
PyLab_Works - PyLab_Works is a free and open source replacement for LabView + MatLab, written in pure Python.
InstaPart - Build circuit boards faster with parts delivered in <24 hrs
LabVIEW - LabVIEW offers many of the functions you'd find in a traditional script-based programming language presented in a more intuitive visual interface ideal fo engineering.