QEMU

"QEMU is a generic and open source processor emulator which achieves a good emulation speed by using dynamic translation.

QEMU has two operating modes:

* Full system emulation. In this mode, QEMU emulates a full system (for example a PC), including a processor and various peripherials. It can be used to launch different Operating Systems without rebooting the PC or to debug system code.

* User mode emulation (Linux host only). In this mode, QEMU can launch Linux processes compiled for one CPU on another CPU."

http://fabrice.bellard.free.fr/qemu/

http://fabrice.bellard.free.fr/qemu/about.html

http://fabrice.bellard.free.fr/qemu/download.html

http://fabrice.bellard.free.fr/qemu/changelog.html