VeroRoute - Cross-platform software for producing Veroboard (stripboard), Perfboard, and single-sided PCB...
myOpenLab - MyOpenLab is a platform for finished elements (program components) that can be linked together.
Virtual Breadboard - It is a circuit simulator on a virtual breadboard.
PyLab_Works - PyLab_Works is a free and open source replacement for LabView + MatLab, written in pure Python.
KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
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.