Not an ad. As I know, the most widespread MCU simulator is PROTEUS. You can virtually run your hex at AVRs, PICs and even ARM7. Analog circuits simulation is not perfect, but acceptable. There are build-in SPI and I2C debuggers, signal generator, scope, logic analyzer and so on. Look for prices at designers` site :
http://www.labcenter.co.uk/Also world-wide-web is big place…