Softgun is an embedded system simulator. It is Intended to help developers of embedded systems without real Hardware. It can simulate ARM9, Atmel AVR, and Renesas R8C/M16C/M32C/RX CPU's. It runs on Linux hosts. With some restrictions it runs on Cygwin and FreeBSD.
I have not used it yet but the concept seems good and the CPUs listed are in the main stream. I return after playing with this.