Virtual Breadboard - It is a circuit simulator on a virtual breadboard.
VeroRoute - Cross-platform software for producing Veroboard (stripboard), Perfboard, and single-sided PCB...
VeeCAD - VeeCAD takes a schematic generated netlist and assists you to build a layout - on strip...
BlackBoard Circuit Designer - Help building prototypes on so called breadboards easily
DIYLC - Free multi-platform schematic, layout and guitar wiring diagram editor
KiCad - A Cross Platform and Open Source Electronics Design Automation Suite