Simuino (uno, mega):
https://code.google.com/p/simuino/
Fritzing:
Virtual breadboard:
http://www.virtualbreadboard.net/
Simulator for Arduino:
http://all-about-embedded.blogspot.hu/2012/07/arduino-simulator.html
Simuino (uno, mega):
https://code.google.com/p/simuino/
Fritzing:
Virtual breadboard:
http://www.virtualbreadboard.net/
Simulator for Arduino:
http://all-about-embedded.blogspot.hu/2012/07/arduino-simulator.html