VirtualBreadboard is a simulation and development environment for embedded applications that use microcontrollers. It is easy to use and can replace a protoboard for experimenting with new designs.It is a freeware.
VBB simulates many of the PIC16 and PIC18 microcontroller devices with now Arduino emulation. In addition a wide variety of simulated components such as LCD’s, Servos, logic and other IO devices that can be used to model and simulate high level circuits. See More Here