gpsim

gpsim is an open source simulator for Microchip's PIC microcontrollers. It supports all three families of PICs: 12-bit, 14-bit and 16-bit cores. For more information, visit http://gputils.sourceforge.net/

Click here for tutorial on gpsim

Real Pic Simulator

Real Pic Simulator is a professional PIC simulator for Microchip’s PIC microcontrollers. The simulation process is done in real time with user interaction through different visual components. The main goal of this project is SPEED. The developer also claims this as the fastest PIC simulator. For more information, visit http://digitalelectrosoft.com/

PIC Development Studio

PIC Development Studio is a simulator for the PIC16F84 microcontroller. It also provides a plugin framework making it possible to develop custom components. A library of ready-made components is included. For more information, visit http://picdev.sourceforge.net 

PICsim

PICsim emulates microcontroller PIC16F628 and peripherals such as USART, EEPROM, WDT, and timers. The simulator architecture permits easy implementation of external elements in C language. PicsimLab1 is a real-time emulator of a development board. For more information, visit http://picsim.sourceforge.net

Arduino

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It is intended for designers, hobbyists, and anyone interested in creating interactive objects or environments. For more information, visit: http://www.arduino.cc/

OSHON Software Project

Here is a collection of software from oshonsoft for different simulators. It consists of simulators for AVR, PIC, PIC18, PIC10F, Z80 and 8085. For more information, visit: http://www.oshonsoft.com/