Virtual Breadboard is a free circuit prototyping software that has readily available hardware and software simulation tools. It can simulate various hobbyists microcontrollers including the popular Arduino, and the Parallax Basic Stamp.
As shown below, this software not only simulates the Arduino hardware but also runs the software in the virtual microcontroller.
See the video here: Virtual Breadboard – Arduino Demo
This could become a tool of choice for roboticians building and testing custom circuitry for their robots.
Via Hack n Mod.