BootChamp

BootChamp is a small utility for quickly booting into Windows on your Mac.

FAUMachine

FAUmachine is a virtual machine, similar in many respects to VMWare[tm], QEMU or Virtual PC[tm].

Test your LiveCD on Windows without burning it to a physical CD-Rom

Virtualization Manager Professional - Overview

It is a generic machine emulator and virtualizer.

Simple and powerful virtual machine for Mac. Mac virtualization software. Learn more about VMware Fusion and try it free today.

Wineskin is a tool used to make ports of Windows software to Mac OS X.

Bochs IA-32 Emulator provides a virtual PC that can run operating systems such as Windows, Linux, and BSD.