Qemu

When used as a machine emulator, it can run OSes and programs made for one machine (e.g. an ARM board) on a different machine (e.g. your own PC). By using dynamic translation, it achieves very good performance. When used as a virtualizer, it achieves near native performance by executing the guest code directly on the host CPU. it supports virtualization when executing under the Xen hypervisor or using the KVM kernel module in Linux. When using KVM, it can virtualize x86, server and embedded PowerPC, 64-bit POWER, S390, 32-bit and 64-bit ARM, and MIPS guests.