Also included: Compatibility Layers and Dual-Booting.
DOSBox for Intel-based and PowerPC-based Macs. Virtualization environment for DOS.
VirtualBox for Intel-based Macs. A true Virtualization environment running many different OSes.
QEMU – Open Source CPU emulator for Intel-based and PowerPC-based Macs.
Darwine – for Intel-based and PowerPC-based Macs. Compatibility Layer.
Apple’s Boot Camp: Free/Beta dual-boot environment setup for Intel-based Macs. When Mac OS X 10.5 “Leopard” ships, this will no longer be free.